I too am very very disappointed in the VP150!
I notice a large tone difference between the M80's and the
VP150 when using pink noise to calibrate. The VP150 sounds low/muffled even at the same SPL reading as the M80's. I have an old Sapphire center that matches the M80's closer than the VP150. Dialog is terrible unless I up the center by +5, even then its more loud than understandable. I spoke to Axiom and tried all suggestions to no avail.
And I also notice my QS8's match the M80's better than the VP150?

M80s,VP150,EP500,QS8(4)