Inexpensive Multichannel 3x Amp for HT add-on

Expanding my 2-ch system to be switchable to a 5.0 or 5.1 system for home theater. Front R&L are my Maggie 20.1's, biamped through VTL 450's and a Bryston 4bST, a Hovland HP100 preamp... I don't believe in spending alot on HT, so here goes:

I plan on using Maggie MMG-W's for surrounds and MMG-C for the center. I'll need a pre/processor, and am thinking of a used Outlaw 950. I'll need a 3-ch amp for the center and rear surrounds. I don't want to spend more that $600. I'll run the 20.1's full range with pre/pro output thru the Hovland and forementioned setup. Maybe someday I'll get a sub for the earthquake scenes. Like I said, I don't want to go overboard on the HT expenditures.

Any suggestions for a decent 3ch amplifier, and perhaps other alternatives for the pre/pro?

Thanks in Advance, PS
In looking around, what surprises me (on Ebay) is how much people are willing to pay for some basic multi-channel amps. Just shows to go you how much home theater is pulling ahead. Crazy! I might be better off buying two stereo amps and ignoring one channel!
A solution I have used for several years was 3 Outlaw mono amps for my surrounds. HT is less important for me, thus the use of simple SS amps. I recently sold two of them for $200 each, so $600 for three should be available. Good luck!
Audio Refinement Multi-3 would be a good choice in your budget. You may even get a bundled deal with the AR Pre-DSP. Alternative would be a 5ch amp from Adcom, GFA 7500.