The speaker and room size are important. I loved the 1.6s, but don't be persuaded to get them because everyone says how great they are. Sometimes the smaller Maggies work better than the bigger ones in smaller rooms. I was a naysayer regarding the importance of room size, but learned the hardway that the 3.6s were too big for my room. The MMGS are a fine speaker and work great in small room. I've owned the MG 12s, the 1.6s and the 3.6s. One other option you may consider is Peter Gunn's modded SMGAs. I've heard them on two separate occassions and was unduly impressed with them on both occassions. If I go back to Maggies, this is the speaker I would get. It was the most "musical" of all the Maggies I've heard. However, this is was a modded SMG. You can email me if you want more info.
Amplification: Its not just the wattage, but the current an amp can deliver. Damping factors also play a role. The fact is, it takes a lot of juice and good damping to get control over the panels to make the Maggies sing. Nonetheless, there was a guy who was happily running his MMGs with a Music Reference RM 10, a tube amp with 35 watts of power. This is all hearsay, but I understand he had a moderate to small room and listened to mostly chamber music. He moved on to a set of tube monoblocks with 70 watts per channel (I think) and was much happier. He did tell me there were times he really wanted to crank the volume, and though he never had any problems with clipping (a testament to the Music Ref amp), the amp did run out of steam--just wouldn't play any louder. Regardless of the model Maggie you choose, you may be temporarily alright with your current amp, but you should factor in that you will be getting a higher powered amp in the future if you intend to stick with Maggies.
Just my 2 cents.