In fact I did try the Onkyo as a renderer, but when compared to the other solutions, I find it, as you said too harsh, and with a much narrower soundstage, so I dropped this completely.
As for using 2 amps to power my fronts, I use a home made splitter where I have a small box with 2 pairs of female bananas from the amps and I manually plug my speaker to one or the other... Archaic, but cheap and working...
That being said, I very recently did try to bi-amp my speakers (old french made Elipson Axial 160), using the Onkyo 818 (5.1 is good enough for me); Then, I now find this solution being slightly better. I need some more listening to make my mind, but so far I feel the sound more detailed as well as more responsive, so I may put the M-508 on for a well earned retirement!
I have an older laptop that I have connected to my network and to the Oppo through the USB asynch and usually command it from the Gizmo app on my Xoom.
I manage my library through another computer in the office, on which I do all the tagging and such. Both computer have their own libraries, but the one connected to the Oppo is just auto-importing the additions or changes I make on the files with the office one.
This allows me to keep the files only in one location: a NAS in raid 10.
Let me know how it sound, my next step will certainly to drop completely the receiver and use it as an amp for the subs and center while I'll invest on a better amp for the main, Bryston being a candidate with the 3 or 4 BSST2.
Cheers