The problem with the downward center sound you are encountering is that the VP150 is 6 ohm speaker and the M2 is 8ohm, unless you have one of those speakers on it's own amp with a volume adjustment, the VP150 will always be playing louder by about 1-2 db.

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