Have you recalibrated all of your speakers with the addition of your vp150 so they are all at 75dB's? If you still are using the same settings within the receiver for distance/dB levels/etc... and have not recalibrated, this could be the issue. The vp150 is a 6ohm design, not sure about your prior center.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85