So I found an individual who is selling a Vintage Ampeg SB-12 Portaflex. He has it listed for $600. I have already requested to see more pictures of the amp due tot he fact he only has 2 posted. My question: Is this a good deal? Should I ask for a lower price? What is a typical price for one of these that is in decent shape, and works as it should? Thanks for your all's !