Well here is something you can try for free, take your 5 channel amp and use it for your front speakers only. One channel will drive your center speaker and the other 4 channels will bi-amp your mains. This can sometimes (not always) make a big improvment. Take some cheap lampcord wire and listen to your speakers as they are hooked up now, then hook it up and listen with same cheap wire in bi-amp, if they sound a lot better bi-amped then you may want to consider this and add a two channel amp for your rears. Set your rear speakers to none for this test on movies and try two channel music also with just your Front speakers in play. I at one time did this with a system I had and had huge gain in sound quality on that system, YMMV.
Additional amplification?
I am considering adding a seperate 2 channel amp to my current multichannel setup, which is: Outlaw 950 pre/pro, Marantz DV 8300 universal player, Rotel RCD 1070 cd player, Rotel RMB 1075 (125wpc X 5) amplifier and Monitor Audio Silver S10s (fronts), Silver center and Silver S2 surrounds. I listen to music about 85% of the time including DVD-A/SACD. Will a seperate 2 channel amp make a difference? I like a crisp, somewhat bright sound in my music. Considering Rotel RB 1080 (205wpc), Parasound 1500a (200wpc. Suggestions and opinions would be greatly appreciated.