Personally, I would stick with the VP180 on its own. The problem with the dual configuration that you describe(M2 & VP180) is that because of the difference in SPL efficiency ratings between the two speakers, there very well could be a slight difference in volume levels(VP180 will probably be louder) which kind of defeats the whole purpose of this particular set-up. I faced that issue when trying an M2 with the VP150 which was considerably louder so I scrapped the experiment.
The only way you can deal with that, of course, is by having them driven by separate amps or a switch where you could control the volume of at least one of the speakers to obtain balance.
