Anybody else using AV880x as 2 channel preamp?

What are you trying to accomplish here? Are you trying to add a dedicated stereo preamp with HT bypass for your 2ch music listening into the mix? 

While the Marantz AV8802 is great when used as a surround processor for surround sound movies or HT but its stereo performance for 2ch music playbacks are lacking compared to high end AV preamp surround processor such as the Classe SSP 800, Classe Sigma SSP, Cary Cinema 12, Bryston SP3/SP4, McIntosh MX160, Meridian Reference 861 v8, Krell Foundation, Krell S1200U, Krell Evo 707, Audio Control M9/M7. 

I haven't heard the AV8805 though. 
If you really care about 2ch performance for music playbacks I suggest that you get a dedicated stereo preamp or stereo integrated amp that has HT bypass. 

Or if you want a single AV pre pro that can perform really well in stereo I would get something like a used discontinued Classe SSP 800, Classe Sigma SSP, Bryston SP4/SP3, Cary Cinema 12. 
These processors will perform better in stereo than the Marantz. 

@yakbob  

I think the McIntosh's flagship AV preamp surround processors (eg MX150, MX151, or MX160) share very similar analog audio circuitry as the McIntosh stereo preamp such as the C46 preamp, not the McIntosh's entry level AV processors such as the MX120, MX121 or MX122..

Both the MX122 (entry level) & MX160 (flagship) support and decode the latest formats and codecs eg 4K HDR Dolby Atmos DTS-X Auro 3-D. 

The MX122 was based on Marantz AV8802 processor whereas the flagship MX160 is pure McIntosh all the way. The MX160 performs and sounds way better than the MX122 in both stereo and surrounds (HT) and is equipped with much better room correction (Room Perfect) as opposed to Auddysey found in the MX122. 

I've heard that the MX160 shares same analog audio circuitry with the McIntosh stereo preamp but not sure which model I think it's a newer model.