Cool to see some other Promedia owners who moved up to better stuff. Thanks for pointing that out about impedance ccsakura, I don't know how I missed it. A watt into 4 ohms will definitely be different from one into 8 ohms. I'm thinking this will be my first step into a better system, and I will keep upgrading as time and money allows. Seems kind of like what you're doing. The RB-5's should make some nice surrounds in the future.
Juba310, did you try it and see? I hooked up my dad's old Bose 301's to my 4.1's and the sound was fine for me. I think they are rated at around 100 watts and I know they are 8 ohms. I would not want to crank them but never felt the need to do so either. The RB-5's are most likely more efficient than the 301's so what you said seems kind of surprising. If all else fails, I guess I could put the RB-5's away for a bit until I get a receiver.