1-You really should strive to have the same amplification to all 3 front speakers (just like having matching fronts) to get
2-Having dual volume controls involved is a pain. The volumes will never match, period.
3-Don't underestimate the toshiba. If you do a side by side, is it worth using the rotel cd?
4-The rotel will crush the yamaha in quality. Why not sell off the yamaha, rotel cd& adcom pre and put the money into one nice 5.1 pre-amp(rotel, adcom or similar. Its a big step but will make you much happier. Also, think of how much you will save in using fewer interconnects?