Tom,
There's some information on the GIK acoustics web site, and there is a good, brief and fairly non-technical primer on the galen carol audio site (gcaudio.com).
Also there is a forum on the michael green audio web site: michaelgreenaudio.com
I recently bought a roomtune pack from mga and some extra pieces and I know from experience with another, no longer made similar product that these work well. A basic roomtune kit is $375 and may be all that most smaller rooms will need. I've had GIK in the past and they work well, but they can get expensive and from my experience it is tough to get just the right balance with these in a smaller room. The MGA stuff is an entirely different approach, which I used in my last listening room and worked great and for a fraction of the other stuff out there.
HTH,
Jim
Jim Rebman -- recovering audiophile
Equitech balanced power; uRendu, USB processor -> Musette DAC -> 5670 tube buffer -> Finale Audio F138 FFX -> Cain and Cain Abbys near-field).
s.e.x. 2.1 under construction. Want list: Stereomour II
All ICs homemade (speaker and power next)