If music is important I'd find a stereo amp that works best with the ProAc 1.5s and then buy a decent 3-channel amp for the center/surrounds. This way you get the best possible amplification where it's needed most(has its own power supply, not affected by 3 other amps, synergy with 1.5s) and you have the flexibility to upgrade the stereo and/or 3-channel amp as needed in the future. Downsides are possibly higher cost and 2 boxes instead of one, but you don't get something for nothing. Best of luck.
Tim
Tim