What amp would you suggest for Magnepan MG12s

One amp for sure is the Modified Moscode 300 or 600. MOdified is more refined than stock units. But with a few upgrades a stock unit especially the 600 will surprise you. The Odyssey Stratos is another high current amp that should also do a great job on the Maggies. I would prefer to have a tube preamp in the front end with those amps. The amps you mentioned above will work well with the maggies too. If you are a rocker and want to play very loud by all means go for the power. But if you are on a budget the Moscode 600 will make them sing. If you can find one. The newer Moscode amps will do a truly wonderful job too.

If you want the best of both worlds, you can use a solid state amp and a tube pre-amp. That is the more expensive solution that I use with my 1.6's. However, I think that you would be shocked at how good the vintage luxmans sound with the maggies. The R117 is rated down to 2 ohms and will handle the 12's and the 1.6's with ease. Save yourself a couple of thousand dollars and for the price of some good interconnects try a really fine vintage high current R117 receiver (if you can find one in VG condition as the volume pots can go bad)). You can always add a tubed CD player or tube buffer but I don't feel it is necessary as the amp section isn't bright or harsh. If you want to spend a lot more, try a lector zoe preamp and an innersound esl 300 mark 2 amp.

How about Channel Islands D 200 Monoblocks.

I can tell you not trying a Emotiva XPA-5, and a mills resistor is a mistake. More money doesnt mean better. As far as resistors, spend $10 at parts express, grab every size 10w .39 cent each resistor pair from 0.22 to 3.0 ohm. When you find the right resistor your looking for, pick up a mills 12 watt in that size from parts connexxion in Canda for $14 shipped to you. The mills DESTROY the cheap resistors.

I'm using an ARC 150.2 Tripath amp on my 1.6's. It's a wonderful combination. A Vandersteen sub fleshes things out, as well as opening up the soundstage even more!
Magnepan and Audio Research are very good together!
Good luck