The 500 will be more than enough for your room size, 2 will just help even out the LFE throughout the room.

The QS8s will allow you to play them louder so not overkill.

You have picked out a great system, buy with confidence and enjoy!\:\)

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