Purchase a receiver or what? need your advice.

The JC1 has a better input stage and I wanted full monoblock for my front stage (including center channel).  The A23 is fine for surround, but the center channel is the most important.
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I actually got a pair of Bryston 7b3 monoblocks after I determined the Parasound was too slow/warm.  The Bryston went way too far into the resolution/speed.  It's about the highest resolution amp I've heard, but it responds so fast that the sound is there and gone before you can really hear it.  It was not a match in my system and I did not want to "try to make it work" through stuff like gold-plated interconnect and cables.  It actually could not keep up with my Emotiva in body and volume! 

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The Classe amplifiers were on my list, but a couple things put them down further on priority.  One was silver color (though I could try to get CT models that had a black front).  The other was the fan - I did not want to deal with a fan after years of usage.  I will keep them in mind, though, and let you know if I decide to try another amp.  My Parasound JC1 are fully loaded with all silver fuses now and I think that will get me to where I want.
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My 1080p sony VW95ES projector is so good that I do not actually feel any need to upgrade to 4K at this time.  It would be a minimum $14k investment to do that, since it would be at least $10k for a decent 4K projector and another $3.5k for Lumagen video processor.  This doesn't include any expense for Oppo or other 4K bluray - and I would have to look at my processor, which does not support 4K. lol.  If I were to do this type of thing in the future, I would probably get the latest MArantz (i.e. AV8805) and then start pulling the guts out and rebuilding - putting in faster op amps on digital I/V board and upgrading all caps to something like Nichicon KZ, etc.

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I have thought about full range towers for my left/right, but I would first have to build new subs (which is an idea on the list).  My subs are just about the same exact size of a SVS PB16-Ultra (massively huge) and towers would not really work for optimum positioning in my room.  My current subs are about 28" deep and  I would have to build taller and shallower subs so that I could place the towers in front of them and still keep the proper position and room acoustics. lol. 

Regarding the 4K thing, I have had people come over and see my projector and their comment is "that's 1080p?!?! Really???".  The image actually looks so good, it's pretty much just like film.  I'm sure that a good Sony 4K projector will be better than what I have, but it is also based on source content.

@auxinput

Wow! Your subs are massive 28" deep. What drivers are you using for your subs? I’m also using 2 subs in my dedicated theater room.
Are you also using subs when listening to stereo music?

Sony makes one of the best movie projector only bested by Runco.
When you go 4K route you should get the Oppo 203/205 in used markets but I suggest you wait a little longer cause it isn’t worth paying for the Oppo 205/203 for 3 times their original MSRP. That’s how much they are charging them for these days in after market ever since Oppo ceased productions and operations. Those people are just trying to take advantage or trying to rip people off.
Lucky me I have purchased the Oppo 205 late last year and only paid its original retail price of $1300.

I’ve heard that the new flagship Pioneer Elite 4K UHD bluray player is coming soon to North American market but I think they are going to retail for around $2500. Not sure. But heard rumors that the build quality and audio and video performances will be on par with the Oppo 205 or perhaps even better, dunno. I think they were already launched in Japan/Asia and Europe. Can’t remember the model.
Few people also told me that the somewhat new Sony ES 4K UHD bluray player (1000ES) is very good also and its audio & video qualities over HDMI are probably on par with the Oppo 203/205 but the Oppo 205 has superior DAC, analong audio stages & power supply.

As for a new pre pro that supports 4K and stuff, you can always run the audio only HDMI out from a 4K bluray player to your current pre pro and the video only HDMI out directly to a 4K display or a 4K Lumagen video processor. And if you have a 4K capable cable tv box or some sort down the road in the near future you can run the HDMI directly to a 4K display or a 4K Lumagen video processor for video only and run spdif or Toslink out to your current pre pro for audio only. I think you can keep your current Krell pre pro and no need to get a 4K capable processor.

But if you must get a new 4K capable processor the latest version of Krell Foundation series supports 4K but not sure if it supports the latest HDR and Dolby Vision and hdcp 2.2 necessary from a 4K UHD bluray player. I think the new Marantz AV8805 supports the very latest formats. The Lyngdorf MP-50 and the new latest NAD M17 v2 processors also support the latest formats. Even the Anthem AVM60 does not support Dolby Vision and latest HDR. So far I think the new Marantz AV8805, NAD M17 v2 & the Lyngdorf MP-50 are the only processors currently available on the market that support the very latest formats on the video side. The revised or latest version of Classe Sigma SSP Mk2 supports 4K, hdcp 2.2 but does not support HDR nor Dolby Vision. I think the new Bryston SP4 supports the latest formats too.

Not even sure if the Classe Sigma SSP Mk2 are still in production especially there are uncertainty with the brand after it was sold to Sound United early this year. Not sure if the Sigma series are still in production.

Many hifi reviewers claimed that the Krell Foundation, the Classe Sigma SSP and the NAD M17 are superior sounding to the Marantz AV8802 but don’t know how they would compare to the new AV8805. Last year I have personally compared my previous Classe SSP 800, Classe Sigma SSP & the Marantz AV8802 in my own home theater setup. For surround sound movies (home theater) via their HDMI inputs, the SSP 800 is the best, followed by the Sigma SSP and the Marantz AV8802. But when used as an analog stereo preamp for music playbacks in bypass mode, the Sigma SSP is number one, followed by the SSP 800 and then lastly the Marantz AV8802. But the difference between the Sigma SSP and the SSP 800 was subtle, they are pretty much on par. I found the Marantz 8802 to be lacking when used as an analog stereo preamp for listening to music in bypass mode.
Then lastly when I compared these 3 processors as stereo digital preamps for stereo music playbacks, the Sigma SSP, fed via its rear USB input, by far way outperformed the other two processors, then followed by the SSP 800, fed via its spdif, then lastly the Marantz 8802, fed via its USB & spdif. The SSP 800 does not have USB inputs. Its rear USB port is only for loading firmwares.
So the Sigma SSP is a king when used for stereo digital music playbacks fed via its USB input in comparison to the other 2 processors. The SSP 800 was pretty good too when fed via its spdif and even HDMI inputs for stereo music playbacks or when used as a digital stereo preamp. The Marantz 8802 could not quite compare to both Classe processors in this area. The DACs in both Classe are also superior to the Marantz 8802.
But when used for surround movies (via HDMI) the Marantz was very good especially for the money since its original MSRP was the cheapest compared to both Classe’s original MSRP. I could probably easily live with the Marantz 8802 when used strictly for home theater (surround movies) and it isn’t far behind than the Sigma SSP.

I have also also listened to the NAD M17 briefly at my local dealer in an unfamiliar setup so had no idea how the NAD M17 would compare to those 3 processors. But the M17 was very good.
I have not tried the Krell Foundation series processor but it was highly praised by some hifi reviewers.

In regards to the Classe Delta series amplifiers I really like the styling and color actually. I hate the CT series styling I think they are the ugliest amplifier I’ve ever seen.
But regarding the fan, they are pretty silent and almost inaudible depending on how far back you sit from the amplifiers and how big your room is. But the filter needs to be cleaned every once in a while. There’s a detector where the light flashes on it means that it tells you that it’s time to get it cleaned up.

If you like black or darker color amplifiers, Classe is probably going to finally launch the new replacements for the Delta series gears that were supposed to be launched summer of 2017 but since B&W Group decided to shut down Classe’s main facility in Montreal last fall so these new Delta series gears weren’t moving forward with productions. But I’ve heard a rumor earlier this year that Classe now under Sound United are going to launch these new Delta series products maybe next year. I have heard the pre-production run of these new Delta series gears at last year’s Music Matters at my local dealer. They consisted of a new Delta Pre stereo preamp/DAC to replace the recently discontinued CP 800 stereo preamp/DAC and the new Delta Mono monoblock amps run in class A mode at least for the first 50 watts or so and the remaining in class AB. They were very dark charcoal colors. They look different from the existing Delta series gears. They drove the B&W 800 D3 at the time and I found them to be better than the existing or recently discontinued Delta series combos, which are already pretty amazing epecially the CAM 600 monoblock amps. The new ones were better maybe due to class A operation. The expected retail price of the new Delta Pre stereo preamp/DAC was around $10k ish. And the expected retail price of the new Delta Mono monoblock amps was somewhere around $20k to $30k per pair. In comparison to the existing or recently discontinued Delta series combos the new Delta series gears sounded more liquid and fluid more refined and yet maintain high resolution, details, transparency. Overall they sounded more musical than the recently discontinued Delta series gears. They had better rhythmic drive and subtle dynamic shifts better midrange bloom and better body textures and volume than the existing Delta series combos. They sounded more natural and organic to me on those B&W 800 D3. They sounded spectacular together.

Well, if I can't get my Parasound amps to a level where I'm satisfied, your buddie's three CA-M600 amplifiers are definitely an option, especially if he's willing to sell for $7-8k.  I should know within a couple weeks if these Parasound will work out with the silver fuses (need to burn them in, as they were just put in last Friday).
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As I have said, I feel no need to upgrade to 4K at this time.  To me, the sound is much more important right now.  Upgrading to 4K will be way down on the priority list.  In 5 years, I might feel differently, but a $14k expense is too much for me right now.
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Yeah, stock, the Marantz AV8805 is not going to be as good sounding at the Krell Foundation or Classe Sigma (I have not heard the NAD).  However, I will avoid anything with op amps if I possibly can.  Even though the Classe is good, it's not going to be good enough for me.  The Marantz AV8805 has an excellent base architecture with its massive power supply and discrete analog output stages.  However, it can definitely be improved upon.  I'm not sure where the future will lead me, but I believe my Krell S1200 will still sound better than pretty much anything out there (it's just that the consumer market places so much value on 4K and Atmos and every new thing that comes out).

Oh, just re-read your post.  It sounds like your buddy only has two CA-M600 amps.  There's actually a guy on audiogon selling a pair of black CT-M600 for $7580.  Unfortunately, I would really need three amps, and it will be much harder to find a single black M600 than it was to find a single black JC1.  I was looking at them when I pulled the trigger on the Bryston 7b3 amps, but I have since redirected my focus back to JC1s (which I now have three). 

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I did not upgrade to Oppo 203 because I mainly use it for a transport and the 103 still has Netflix streaming (which I do a lot of).  The Oppo 103 is still the absolute best transport for Netflix streaming, and I do have the linear power supply upgrade.