Hello -
I have the MMG's as well as other Magnepan's and all I can say is that, given that the sound quality of the amplifier/receiver is high, the more power the better. I actually powered some MMG's with an NAD 762, and it sounded great, but when I moved on to better and more powerful equipment, such as ARC, Sunfire, B&K, and McIntosh the difference was night and day. Given a budget, I would recommend doing this:
1) Get a good subwoofer because the MMG's provide little to no bass.
2) Get a a preamp and a amplifier versus an all in one unit.
3) Run the Preamp out into the sub, and out from the sub to the amp.
I have done this, and I know that there are lots of varying opinions on it, but it made all the difference in the world when I was using the MMG's. You are effectively using the crossover on the sub to cut some of the signal to the amplifier, making for a more efficient use of its power. The MMG's can't produce low frequencies well at all, so I say, cut it out of the equation and let the sub do the heavy lifting. This setup sounded amazing! I know it might be hard to find seperates for a good price, but it may be worth slowly building up to. Check audiogon.com for items from proceed, which mark levinson had something to do with, or from older carver units. There is an interesting amp out and available on ebay called a Sunfire SZA-2200. It is equal in power to the 2 you mentioned and it is a Class T amplifier similar to the one used in the Audio Research 150 series. I owned one and it was excellent. You can pick one up for around $200-300, and then just get a nice preamp like an Anthem TLP 1 fr around $400, and you are almost there. All you would need is a sub with a left and right in/out and adjustable crossover and you are golden.
-Wes