i would say go with the vp-180 and M60's all the way.
as far as what you will gain..
side
this is only a physical comparison.. I had a VP-150 for many years, however when i recieved my 180.. it was a night and day difference... I sit 13 feet from the center channel. The intigration between my M60's and the 180 is almost perfect. The 150, is simply unable to keep up with the M60's.. I would say that the 150 would be a good match for the M22's.. However if you set up to towers then a 180 would be worth the money... I would actually wait on surrounds... keep in mind 70% or so of the sound in a movie come from the center channel... depending on how much TV you watch, few shows today are in true surround.. some are, and of those that i have experienced are not mixed that well...
If i was in your position, i would go for the 180/ M22's over the M60's and the VP-150.
if your budget will support the M60's and the 180, you can always move the M22's to perform surround duty.
Right now i have my M60's and VP-180 crossed over at 40hz, and set to large... This is partly due to my EP-600 amp being dead, and at Axiom, until i decide to buy a new amp.... however, even after the 600 is working again, i will probably stick with the 40hz cross over point.
Kind of long, but i tried to cover everything for you. I hope this helps.
