What is the minmimum room size for Magnepan?

I do not think my Plinius has enough power with 175 watts into 4 OHMS, I would guess around 400 - 500 watts with a lot of current would max them out.

I know this sounds like a lot but I would like more power with my setup, and the Innersound setup never sounded strained at all with 1000 watts, so somewhere in the middle is my guess.

The Maggie 1.6's require oodles of power to sound right. I used a pair of 1.6's powered by a Spectron Digital One (500 wpc into the 4 ohm load...1 KW total power!) and the speakers never ran out of power or had anemic bass as others have often commented about. This is a speaker where wattage should be the primary consideration when selecting an amp. I also used a tube preamp, which gave the set up a much smoother sound, in my opinion. Happy Tunes!

I've owned two pairs of Maggies - a very early model that I bought in the mid-70's and a pair of 3.6's that I got last fall. The 1970's version sounded great until it failed when it was about 6 years old from what I was told by the factory was an overly UV-sensitive glue. The 3.6's are delightful. I use them in a room that is about 14x20 and (just to enter into the power debate) I started off running the 3.6's with a 100 watt solid state amp, decided I needed more power, switched to a 350 watt SS amp, which definitely sounded better - but now I'm using a 100 or so watts per channel tube amp (all McIntosh amps), which sounds the best of all. I'm not sure whether the differences among the amps had to do with raw power or just to better design as I moved from one to the other. Bottom line from my experience is that different things work, some better than others. I suspect that quality of design (whatever that means!) trumps raw power with these speakers. Try to buy at a price that won't hurt you if you decide to experiment with something else.
Skip

I have a pair of 1.6s in a smaller room. That means the seating is closer to the speakers, so the speakers are closer together for good soundstaging. Patience and careful adjustment definately pay off and the maggies are just fine. In fact, I like them better in the smaller room because, to my ear, the bass sounds better. I drive them with a Sonic Frontiers Power 2 with no problem and find the maggies tube friendly if the amp is big enough. I do agree with Fatparrot and Philjolet that wattage is a concern, and with solid state amps, I think the larger the better if you really want the speakers to sing.

Lots of good amp choices out there - Classe, Aragon, Marsh Sim Audio and Bryston to name a few. Regardless of which Maggie model they all like to have lots-o-current running through them. A Bryston 3B would be plenty powerfull enough for a pair of MMGs and might do an effective job on the 1.6's but a 4B would do a better job with larger models. If you are really looking at the 1.6 model then look for an amp that does at least 300 w/ch @ 4 ohms (Maggie's nominal impedence).