Separate Amp for AV receiver

OP, you have a nice 2 channel system, but you can’t compare your mid Fi HT components to premium priced 2 channel equipment and make a valid comparison.  It’s like expecting the same performance from a Hyundai Sonata and an upscale Mercedes Benz.  Since you like McIntosh why not get a receiver or Pre/Pro from that company and then make a comparison?

Stereo (2-channel) is stereo, HT is HT, and never the twain shall meet.....I have three HT systems, two based on separates, one with an AVR. They are hardly ever used for music listening, maybe FM once in a while. I will have to admit that AIX discs in multi-channel format can sound pretty goodon a higher-level HT set-up, and all concert DVDs/Blu-Rays benefit from the format also. The trick there is that video is part of the mix on those discs, soit's akin to watching a movie (ever notice how music sound-tracks in movies usually sound pretty damn good?). The eye-candy enhances the audio portion and vice-versa.

Ok, lets take a look at ur HT speakers, what are you using ? Do you have subwoofer(s).
does the system lack slam ? If its HT ya gotta have slam, slam is where the money is Lol. Sounds like you have a nice 2ch system

Lets look a little closer at what its NOT doing for you, HT seems pretty straight forward, hook up all the speakers and bam its a HT, not always…..

Alright, I've decided upgrade the speakers for my HT first, they are twenty+/-. I started with a new subwoofer. Just installed a new REL 7X. I also have a REL S/3 SHO for my two channel system, along with my 803 D3s, so I would like to go with both subs by connecting my Denon AVR4300 direct with the REL 7X, and using the "Longbow" REL wireless connection to the S/3 SHO. I can't seem to get them to pair although I've tried multiple times.
Anyhow the sound is much improved with the new 7X. My front speakers for my HT are NHT 2.5i, very efficient speaker. The rears are ceiling mounted Klipsch, don't know the mod. #, but they have three speakers facing down, front and rear. The upper clg. mtd. fronts are Boston Acoustics with front facing and rear facing speakers. The Center channel is Martin Logan Motion 50XT.
I think I'll keep the center channel, it's only a couple of years old, but change out the upper rears, and upper fronts first. 
Please advise, what do you think.
Thank you