I'm not sure what a GSA auction is, but from what I've read in the replies, it sounds like a government auction where they get rid of stuff so they can spend money on buying new stuff. In my area, I've been watching the local counties and cities, which list their auctions on this site.
AuctioneerExpress.com
I haven't been yet, but have been curious about some of the items. Nothing that I have to have yet, but some of the prices have been pretty good.
Eddie