Just found a Marshall Lead 12 in a pawn shop. It's very dirty & missing 3 knobs, but no tears or dings or rips in the speaker cloth. It sounds a little scratchy like the pots could use a good cleaning, but decent otherwise. Asking price is $150, but the salesman said he could get the owner of the shop to go much cheaper. What would be a good price to shoot for? I'm thinking no more than $75 because of condition. Opinions?