I agree in part and dissagree in part to the previous post. To achieve what you're looking for would require a 2ch. pre, with 2 inputs. One input for 2ch, then one as a piggy back going into the processor for Ht SS. When you switch inputs;you have either good 2ch--or HT. I do this,this way. (No ics or speaker wires to change--just the input selector) The quality of what you power the center and rears with/from?---Lots of good used amps;here. I use half of a decent 2ch amp for my center. Nothing matches in speakers or amps; but all sounds good enough for me in ss.
Preserving high-end L and R while going surround
I want to integrate my good 2-channel amp and speakers into a surround system--plugging the L and R outs of a surround SACD player into it, (as the L/R fronts are the most important channels), and buying a "modest" surround amp to cover my center, sub, and rear needs. A modest (=inexpensive) surround amp should be fine for the rears, as I listen to Classical and the speakers will only add ambience that ideally shouldn't be heard--no need for a lot of power or fancy electronics. But what about the center: in discreet surround will the center material be, er, discreet enough not to reveal differences in amp quality?