Best Cheap Amps for Magneplanar Speakers

Look to Wyred integrated amps. Match well with my .7's. I've owned several pairs of Maggies over the years. I will tell you this, the more quality "power" the better the sound. This may be true with other speakers but never as much as Magnepans...

If you are truly looking for a cheap amp....
$400,  I like the Old Sumo Andromeda II or III...(III might be $500)
$900,  I like the Muse Model One Hundred Sixty
These will both make maggies sing

I don't know what you call cheap, but I have had $300 qsc 1450 behind mmgs, and it put out clean, undistorted sound at concert level.  The lights in the house were dimming with pounding bass drums. I had an adcom preamp between source and qsc.  Mmgs were without fuse and sounding good, and the qsc was not even at 1/2 full volume.
It's cheap, something to try.

Class D SDS 470c can find them used for around $400.