You can buy a new 2.1 for about six and a half, so a used 1.6 should be around 4 bills I would think. Great little amp. I've got a 2.1 that I bought used for $500. I love it.
I was going to suggest that you check on www.prepal.com but the don't track prices on used Stewarts... My next step is to look at closed auctions on eBay or visit www.musicgoround.com
This is total newbie question...sorry... but what is musicgoround? I went there and it doesn't seem like much of an auction site... is it just a place for people to sell and buy used stuff? And do they ship? all their stores are midwest/east coast!