I don't like the switching scheme you've just described, feels sloppy, and I don't think you need it, here's why:

You have HDMI inputs, which take audio and video into the surround sound processor, which provides either an HDMI video out, or component RGB (or DVI, or S-Video, etc) video output(s) to the display, audio is either directly to the speakers (if the processor is a reciever and has a amplifier) or directly to the pre-amp(s) over analog.

So I don't know quite what you're worried about, however it shouldn't be a problem. I'd also be looking at Denon, Rotel, harmon/kardon, and Yamaha (in addition to, or in place of, Onkyo).