What amp would you suggest for Magnepan MG12s

Recommend you take a look at the Planar Speaker forum over on Audio Asylum, here ; the server is down today (Monday 1/4) but hopefully will be back soon. The vast consensus in that forum is for a solid state amp which can deliver high current (typically one that doubles power from 8 ohms to 4 ohms, possibly to 2 ohms). Some (including me) pair the SS amp with a tube pre-amp. Maggie typically demos their speakers with Bryston amps at audio shows, in line with Jallen's post. Others recommend various Class D amps (I use an Audio Research 150.2) but Class D also has a lot of detractors, so that's one that requires a personal listen. But if you look at the Forum you will see quite a few questions regarding recommended amps and the related responses, many more than in a more general forum such as this one.

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.