I have the VP150 and VP100 not much difference between them. The Qs4 does the same thing the 8s do just not as loudly, again not much difference. I would suspect(never heard one) the EP175v2 to be slightly less powerfull than the EP350v2 (I have heard) and the EP350v3 is substantially better than the v2, IMO. The sub upgrade, to me, is where the best bang for the buck lies.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70