I have a preamp (norh ACA) for 2-channel that has an A/V pass-through. The signal from the HT part of my system passes though the 2-channel preamp unmodified to my 2-channel amps.
On the HT side I have an Outlaw 950 Preamp/Processor that handles anything HT (DVD player and XBox). It passes all signals to my HT amps - Center, L Surround, R Surround, and to my preamp for Front L and R.
The Outlaw can handle up to 7.1 and does all the processing formats. It is only a preamp (and processor), you will need amps for all of your speakers.
An incredible preamp with A/V pass-through, that would work well with the Oulaw ($800) is the IRD Purist Preamp ($665). You could use the IRD MB-100s as monoblock amps.