Help please upgrading my old Pre/Pro..

Please consider that I have not heard the Classe Sigma or SSP-800. I am just commenting on what I am seeing inside the product.

http://www.audioholics.com/av-preamp-processor-reviews/classe-sigma-ssp-and-sigma-amp5-review/over_sspsigma.jpg

Based on what is inside the Sigma (above), it looks like a trimmed down version of the SSP-800. It only has balanced outputs for left/right. The power supply sections are trimmed down. It seems to be marketed more towards the iphone/ipod consumer group. It will do everything you need, but I would rather put my money on a used SSP-800. There are a few models of the SSP-800:

Single DSP HDMI 1.3 (oldest)

Dual DSP HDMI 1.3

Dual DSP HDMI 1.4

There’s an HDMI 1.4 model on audiogon now for $4200. There’s also a Sigma SSP and an HDMI 1.3 SSP-800 used, each for $3500. Retail on the SSP-800 is $9500.

The SSP-800 might have an edge in sound quality over the Marantz stuff because, based on my reading, the audio stages in the SSP-800 are fully differential/balanced (although they still used LM4562 op amps, the power supply sections are excellent). It’s impossible to know for sure if the audio stages in the AV8802a are fully differential (even though the unit has XLR outputs).  There's definitely enough circuit on each AV8802a HDAM module to do fully differential:

https://www.marantz.co.uk/assets/images/products/av8802/av8802_hdam_board.jpg

Obviously, the Classe is going to be lacking in streaming and decoding/interface support of the new formats.

I think it’s going to be a big guessing game between Classe and Marantz as to which is better. Classe is a small boutique company that only sells so many units per year. Marantz is a giant company with a huge reseller market. The Marantz is going to give you more per dollar for return-on-investment. However, it’s difficult to say which is actually going to sound better.

You can get the Marantz 8802a NEW on ebay for about $3200 (if you don’t care about authorized reseller or warranty). There’s a used one on audiogon for $2600.

Another option I will put out here is one that I went with. I just recently chose the Krell S-1200U 3D after listening and testing multiple very expensive processors. Krell just recently discontinued this model. However, I feel it gives you the absolute best in sound quality. The problems for you:

• No 4K support
• No Dolby Atmos or DTS:X
• Archaic firmware for handling HDMI audio is quirky and can be annoying
• No streaming at all, obviously.

But...

• Superior sound quality from fully discrete Class A based analog stages (2nd only to the Krell 707, in my opinion). This will beat the Marantz and Classe processors in sound quality.
• Has a 3-band parametric EQ per channel. I actually call this a super parametric EQ because it is more than a standard notch filter like a normal EQ. You can apply several different filter types for each EQ band: High Pass Filter, Low Pass Filter, Notch Filter, Low Shelf Filter, High Shelf Filter, Peaking Filter (an alternative to notch). You can read about these in the Krell documentation.

The quirky character of the HDMI audio handling is because the S-1200 does not automatically determine the HDMI audio format and automatically adjust to play that correctly. There are two hard-set audio formats in the Krell: "HDMI A" which is the i2s interface used by DTA-MS/TrueHD and "HDMI S" which is basically S/PDIF over HDMI. To truly have the Krell decode DTS-MA, you have to use HDMI A and have your bluray set to bitstream output. However, if the disc is trying to play 2-channel Dolby Digitial or some weird format, the Krell usually cannot lock onto the audio and you can get a lot of "pops" and "snips" in the audio output. I had to setup 3 different configuration for playing discs in my bluray. Having the Krell decode DTA-MA is truly an outstanding experience, but you have to deal with quirks such as the above or other things like missing secondary BD audio or BD menu sounds. You can always set your bluray to output PCM/LPCM through HDMI instead of bitstream (the setting used to support A/V processors that do not decode advanced formats), and this work well to support any disc, but it sacrifices a -small- bit of resolution in audio for the hires bluray formats.

There’s an S-1200U 3D on audiogon for $3500 (cheapest I’ve seen -- probably because this is normal s1200 that’s been upgraded to 3D). If you choose this route, you’ll want to get a "3D" model that has the latest HDMI 1.4 board.