Hi Rich;
It sounds as though you have the right speakers for the right job: The M2s for critical listening, and the M3s for absolutely everything else!
I guess anyone stating the M3s are warm could be considered just a bit inaccurate at that. I'm guessing that "Warm" has more to do with the bass hump emphasisng the bass a bit. Perhaps the terms "comfortable" "relaxed" or "pleasant" more fit the style of the M3.
And yup, being vertically symetrical is a good thing with M3s; I use all three of mine inverted! The surrounds as well as the center!! Gets the tweets a little closer to the ears at that. Does it help? I dunno; but, it seems as though it...uh...should. (I didn't shave my legs when I rode a bicycle a lot, but some of my friends did, they figured the aerodynamic benifits would make themselves apparent after about 150 miles or so, so...)
Yes, by all means give us an update when you can get around to a good comparo. We're trying to get as good and accurate a data base as we can to be able to give others, with similar questions, the best answers we can!!
(Not to mention reinforcing our own prior decisions!!)
Rich.
