Hidden Gems in Pre-Owned Solid State Power Amplifiers?

I'm with Bigkidz here. They are all for sale for a reason. "That new girl you just met? Someone somewhere is glad that she's gone!" 

There are lots of good SS power amps out there.  Most important thing IMO is to make sure that any amp over 15 years old has been inspected and serviced by a reputable technician.  Some of my favorites (besides the ones listed above):
1- Bryston Power Packs.  If the footprint works for you it's a lot of amp goodness for very little $
2- Adcom.  I like the GFA-555 MkII.  Some prefer the original.  Great cheap amp.
5- Meridian 555, 556, 557 and 559.  I have a 557 and it's a remarkable amp.  Built like a tank.
6- Hybrid amps.  A lot of my friends swear by hybrid (tube input section, SS output) amps.  Moscode 300s and 600s are cheap and plentiful; most will require rebuilding.  Sounds very different from an all SS amp.

+2 on Parasound HCA series.

Some others — McCormack DNA500, Conrad Johnson Premier 350, Sierra Denali, PBN amps

Original GAS amplifiers: Ampzilla, Son Of Ampzilla and Grandson. I have two Son's and a Grandson. One Son is presently making wonderful music with the DCM Time Windows!