Hi bhull,
All of the preceding suggestions are excellent, but keep in mind that if you are using a pink noise test signal to check each speaker, even identical speakers like the M80s will have a slightly different tonal signature depending on the location of each in the room.
Even when you place two identical speakers side by side, then separate them by a foot or two they will sound different with a pink noise signal. For instance, if you replaced your VP150 with a third M80, it would still sound tonally different when you fed each one a pink noise signal.
The combination of direct sounds from each speaker and reflections from the walls, floor, and ceiling, which combine to reach your ears, will vary with every location in the room, causing slight tonal (timbral) changes between each speaker.
Try repositioning your VP150 to different center locations until you can get a reasonably seamless blend between it and the M80s using music, soundtrack or dialog material.
Pink noise is an EXTREMELY CRITICAL test signal and no two speakers ever match totally with this test signal.
Remember too that every room is different--it's "the forgotten component" as an old mentor of mine used to call it.
Try different center locations and be sure to turn off any auto-EQ program that you may have running in the AV receiver/processor.
Regards,
