First comments, based on your setup. Are you using a 3-channel 8008 for L/C/R and a 2-channel 8008 for surrounds? If so, I would switch them around and use the 2-channel 8008 for Left/Right and the 3-channel for surround-center-surround. The 2-channel 8008 has better power supply to drive your main speakers. The surround channels hardly get any demanding signals, so it won’t be as bad of a draw from your center channel audio.
That being said, on the preamp/processor options, if you want stuff such as internet streaming radio / Spotify and the new Dolby Atmos and DTS:X standards, then you have to choose between Marantz and Integra. If you’re not concerned about streaming internet radio options, then Emotiva XMC-1 is an option. Emotiva is working on an upgrade to support Dolby Atmos and DTS:X. All three of these companies have multi-band eq (like a 9 or 10 band equalizer). All three have automatic room correction processes (usually disables the use of manual EQ).
I know Bob said you’d be happy with either Marantz model, but I believe there will be a difference in sound quality. The only reason I would buy the new AV7703 is if I wanted some of the new features Marantz is producing (such as HEOS wireless streaming, etc.). The AV7703 does have the HDAM discrete audio modules, but the AV8802 puts more into this area. Google for internal pics of the AV8802 and you see better power supply and audio module support. You will see that the AV8802 has 13 distinct modules inside from left-to-right to support 13 individual channels. The AV7703 has these all on a single main board and has less of a power supply. There’s more empty space inside the AV7703 chassis. I would even go with the assumption that the AV8802 is going to be better than the Emotiva (Emotiva uses op amp based audio sections and a switching power supply).
There are other options such as Bryston/Krell/Classe, but they may not support everything you want. These are good options for sound quality, but some features may be lacking. Bryston does not have bass/treble/eq/room correction AT ALL (they don’t believe in it). The new Bryston sound (SP3) is also a more laid-back sound that lacks mid/high frequency detail and impact (not my taste). Krell Foundation has automatic room correct (ARES), but no manual eq. Classe does have multi-band EQ, but does not support 4K/HDCP2.2 (if that matters to you). None of these 3 support Dolby Atmos or DTS:X.
I don’t think you want to consider spending over $12,000 for something like McIntosh or Theta Digital. I have read that McIntosh is horribly buggy with their firmware and lack of support. Theta is just insanely expensive.
Sounds like you really want an EQ. If you don’t care about 4K, Dolby Atmos, DTS:X, internet streaming, then the Classe SSP-800 might be a really good option if you’re looking for exotic level sound quality. Otherwise, I’d go with Marantz AV8802. It’s difficult to say which of these 2 might be better.