I'm looking to save a few bucks and get an amp to run my sub. There are a bunch of certified factory refurbished/renewed amps on ebay, and most come with some sort of limited warranty, like 90 days.

Think I would be alright with purchasing one of these, or should I stay away?

 

This doesn't exactly answer your question, but I have purchased several amps from a guy on eBay named Winkasettie. Do a search on ebay for that seller name. He's got a lot more stuff than what he has listed at any one time and I know he's got some seriously powerful Tripath Class T amps for less than $200.
Good stuff.