Having done some blind tests with the VP180 and VP150 with both M100's and M50's, the VP180 is a more powerful performer.

Based on the results of the blind tests, I would recommend using a 100 Hz crossover with the VP150, while 60 Hz is fine with the VP180.

Both the 150 and 180 sounded great (the tweeter arrangement in the 150 works just fine in real rooms), but the probable best choice to go with your M60's would be the VP160. The difference in timbre matching won't be as much of an issue as you might think. For the $$$, a good choice.