I use a two channel preamp with a processor bypass loop. I use a ht receiver which powers the center and rear channels, and send receivers main pre-outs to the bypass ins on the preamp. Many pre-amps including Sonic frontiers, Audio Research, VTL, and Vac have this feature.
I give up on HT
After auditioning several home theater preamp processors and not getting the two channel sound i expected. I took the advice of previous threads and purchased a line stage preamp, I got a conrad johnson model pf-r and life is great. This website has loads of good info if you dare to wade in. Now all i have to do is figure out how to hook up my home theater receiver into the loop.