Using Oppo 205 instead of per amp processor

Now I'm considering a 103D and just running the left and right outputs through the PS Audio piece.  That lets me use the PS Audio DAC for music and the Oppo for movies/multichannel.  And the price point on eBay seems to be super low which is perfect for my experiment.

If I were to get a used 105D, would it work in this configuration --

HDMI from PC to Oppo for future 4K passthrough (I don't have a 4K projector yet) and 7.1 audio decoding
USB from PC to Oppo for higher resolution stereo audio (advantage?)
HDMI out to my Benq W1070 projector
XLR out to my Levinson 333 dual mono amp/B&W N801 speakers
RCA outs for side and rear speakers through a 4-channel amp I have lying around.  I have a pair of CDM2 Signatures and I could easily get another pair.
RCA out to an old sub I have "lying around." (might just make my awesome bass muddy but I'd like to try it)
Can I use it without a center channel speaker?  I'd hate to have to try to get a good enough amp/center channel speaker to match the quality of what I have, but I'm really interested in experimenting with surround.  I guess I could get a Nautilus HTM2 used for around $600 and ponder what to do about a good amplifier for it.

I just bought a PS Audio Stellar Gain Cell DAC and I like it, but now I'm wondering if I should have gotten a 7.1 system instead.  If the 2-channel implementation in this is really good, it has balanced outputs, and I gain the ability to play Bluray discs directly.  It seems like this might be a better choice.  I can still return the GCD if I decided this was better.

To be perfectly fair, I watch more TV than I listen to music.  And although 2-channel of this caliber is pretty awesome for watching television, I wonder what I am missing in side and rear speakers.

I'm afraid that it would just be one big coherence nightmare and sound terrible.  I've been looking for an inexpensive way to experiment and haven't found one.

It took me more than 30 minutes to read the OPPO 105D manual I found online.  Therefore, I can't edit my previous post and I answered some of my own questions.

It appears I can set the center channel speaker to "off."  Can someone confirm that this "phantom" center channel option sounds right/good?

It doesn't appear that the Oppo will pass through 4K, but it does look like I could put it in "audio only" mode, use one of the HDMI outputs from my PC for audio, a different one (maybe Displayport) for 4K in the future, and get sound and video that way.

USB seems like it may or may not be an advantage for 2-channel audio.  Anyone have opinions on this?  The manual says USB is 2-channel only.

The manual isn't really very clear on whether the XLR outputs are the same as the RCA surround outputs.  Can someone explain how this works, exactly?

Right now I stream TIDAL from my PC or use Foobar for high-res music.  I do maybe 60% of my computing on my projector with my keyboard in my lap and my mouse on my little table to the right of my chair.  Quite the computer speakers...

I think I'm going to have to experiment before I can decide what's right for me.  80% of the audio coming from the center channel is fine, but I'm in a dedicated, sound absorbed, very precisely set up room.  If the processor can put the center channel back into the mains and image it well then I suspect it would sound better than having different speakers and amplifiers across the front.