Walt, welcome. My thoughts would be that M60s would be ideal for that size room and that you consider a vertical M2 for a center(likely to result in wider and smoother horizontal dispersion) rather than any horizontally configured speaker. QS4s should be adequate for your room size and should be mounted about 6' up on the back wall and separated about 10'.
The A&B main outs on your 630 are simply a parallel connection to the same amp channel, so no biamping would result. Using two sets of wire from the A&B terminals would result in biwiring, which has no benefit. Unless you use extremely high volume levels the 630 should have adequate power for the M60s, which are slightly higher than average in sensitivity. Most of the time they'll be using about 1 watt, although brief peaks will use much more.
