I'm hardly an expert but here's what I've found.
If you're running multiple inputs (e.g. cable box, roku, BD or DVD player) through your AVR as well as your HTPC then set the TV to 16-235 (usually the standard) and set your HTPC to 3.RGB 4:4:4 Pixel Format Studio (Limited RGB). All the other boxes will expect 16-235 (limited) so putting your TV to 0-255 will throw all your other components off even though it is best for the HTPC.
RGB 4:4:4 Pixel Format PC Standard (Full RGB) is best for an HTPC so if you can avoid the problem above then go for it. Just make sure your TV (and AVR if necessary) can accept 0-255 Full RGB.
On my particular setup I cannot see any difference between YcbCr 4:4:4 Pixel Format and RGB 4:4:4 Pixel Format Studio (Limited RGB). YCbCr 4:2:2 Pixel Format looks bad to me for some reason but I can't quite put my finger on what exactly is wrong with the picture.
I've also found that the commerical BD/DVD players (PDVD and TMT) deal with the color format differently and it's practically impossible to get BD and DVD .iso or disk right and files played back via another player with the same settings. The closest I could come with with YcbCr 4:4:4 Pixel Format.
I do know that when playing a video the color space used internally in the PC is RGB. It doesn't really make sense to have your graphics card change the color space back to YCbCr if your TV accepts RGB. It's an unnecessary conversion best avoided if possible.
All in all it depends on your TV, your AVR if being used for pass-through, what other components you have hooked to the TV/AVR and what playback software you're using. But, IMO limited 16-235 is pretty much the video standard so keeping your HTPC output at that may be for the best.