confused with HT bypass

a fish out of water here, hopefully you guys can help me. i have 2 completely seperate systems in my living room, a 7.2 HT system and a 2 channel system. i did it this way
because i was told that this was the only way to configure it (i'm pretty clueless with HT). but having 4 main speakers, 2 subs, a TV stand and an audio rack in my front room are making things rather crowded to say the least. then yesterday for the first time, i finally REALLY looked at that little switch on top of my supratek preamp called the 'home theater bypass' (DUH). so now i'm trying to figure out if my two systems can share my 2 channel mains and if so how to do it.
To clarify, here are the system highlights. the pre/pro is a denon AVR-1910. this unit has no pre-out so would have to be upgraded. possibly complicating things is the main
speakers i want to use are emerald physics cs2.3's and require biamping and DSP. amps are 2 bel canto S300's.
So let's see if i have this straight in my head. i would go from my new pre/pro's preamp out using only the L and R main pre out into the HT bypass channel on my supratek. this would allow the pre/pro to still control the center channel, surrounds, and subs. the mains signal would pass through my supratek's HT bypass without altering it. obviously i would have to have the bel canto's powered up to get power to the mains as the pre/pro for the mains would only be acting as a preamp and would not be supplying power to the mains, correct? the biggest problem i see is how do i level match the mains bel canto's with the pre/pro's amps controlling the center/surrounds? do i use the trim controls in the pre/pro? would i have enough gain/cut to do this? does the behringer DSP (or the upcoming DBX unit) allow for altering the gain? would i have to 'tell' the denon that i am bypassing the main speakers or would simply using the main pre-outs do that for me? thanx in advance for any help. i would be happy to clarify as best i can if anyone needs more info.