I haven't had a chance to do any serious testing so this is going from memory, but I think I preferred my M2s over QS8s for music. This was almost entirely with 2 channel content matrixed to 5.1 via Logic7, PLII or Neo6. The difference was fairly small but for a music system I would go with M2 (or M22) again...
On the other hand, the difference between QS8 and M2 for HT surround is pretty significant, so even for a 50/50 mix of music and HT I would go with QS8s. You don't lose much on music but you gain a lot on HT.
M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8
| 
