Actually I used the M2 as center because I already had M2s, didn't know squat about multichannel sound, wanted to see how much difference a center channel made, and didn't want to spend any money until I knew more. This pic was taken during a series of experiments with one and two center channels in different arrangements around the TV and was only posted here for the dogs. At the time I normally ran the M2 inverted and vertical on top of the TV where it made a very good center channel; two M2s both inverted and side by side offered more detail (yes I tried to match the volume levels) but there was something I didn't like about the configuration; never figured out what I didn't like hope it wasn't just the appearance
This was the configuration I used the most, along with old no-name towers as surrounds :
I eventually went to a VP100 center anyways; partly for the video shielding and partly because the M2s looked kinda stupid on the top of my TV (the center channel was almost half the hight of the TV). Also went with QS8 surrounds and moved the M2s back upstairs for a bedroom system (now replaced with M40s).
For a music system I would probably have stayed with the M2 (ditto for surrounds), but movies put a lot of content through the center channel so you need a fairly hefty speaker there. In hindsight I probably should have gone with VP150 -- the VP100 works fine but when I look at the energy going through each speaker the VP100 seems like it should hit its limits first.
I do prefer M2s as surrounds vs. QS8s for pure music, although (a) I haven't done proper A/B testing to confirm, (b) the difference is fairly small, (c) I think the difference is direct vs. reflecting not frequency response but again not sure.
It's probably worth pointing out that the M2's LF response is not stellar, so on one hand I have a tough time believing that there would be much difference in sound from the VP100... on the other hand there is a slight but noticeable difference in how the pink noise test tones sound between the mains and the VP100 center, presumably because of the higher bass cutoff of the VP100 relative to the M60s... next time I am really bored I will put the M2s in as mains and see what that changes. I don't think the test tones go through the crossovers so the M60 vs. VP100 difference would be exaggerated; guess I should use the Avia disk instead of the receiver tones for a better comparison.