I'm asking around about dealers. Personally I think you're going to gain a smaller footprint...they won't dominate the room nearly as much as those big M3SI's. They will probably sound a little more refined, maybe a little less "spacious" though, since those M3SI's are bi-directional (with the speakers firing both backward and forward). If you value going a lot smaller with your speakers, but still having great sound, I think it's worth the switch, especially if you shop around and buy either on sale or used.
If you don't mind those HUGE speakers in your new place, you could keep what you have. At least your amps and subs will work with whatever you get.
You may also want to post on Audiogon, they deal a lot with newer and higher end gear there. Not that there's none of that here, just more of it there probably. A lot of vintage audio fans here.