Buying a used amp ATI 1506 or Linn Chakra c5100 or RBH SA-200

I found some used amps for sale, wondering what you guys would suggest is the better buy for a 5.1 home theater setup. I'm using a mishmosh of craigslist finds as my speakers at the moment F - Klipsch KG4 C - Mcintosh cs350 S - Klipsch RF-42 II with a paradigm sub, currently driven by a onkyo707 avr from 2009. My room is pretty small (20x12ft) and I sit only about 8 ft away from the LCR. I'm leaning towards the Linn since I don't think I can take advantage of all the power of a class A 88lb ati amp. He's asking 500 for the linn, I'm going to go listen to a demo today and make sure its in good working condition, anything I should check specifically, and do you think $500 is a fair price, or should I try and offer something for the Ati? The ati seller also has a pair of rbh sa-200 hes selling wondering if those are good for LCR purposes particularly the mcintosh cs350 as it seems to want more power/headroom. Thanks for your help.