I have also purchased several used amps through a variety of sources. I think if you do your homework and try to verify your purchase is from a reliable seller you can do alright. While I have never bought from Audiogon I know many others who have bought from there repeatedly w/o any problems.Once you buy something just take your time to check it out and clean it if needed before hooking it up to your main gear.

The cost savings can be significant and you might be surprised at the deals you can find when the buyer is motivated to just get rid of the gear.

Good luck!