I've got $378 and change credit on Monoprice from a return I did a few weeks ago. I was hoping they'd get in GTX 1070/1080s, but it's looking like that's not going to happen. They have all sorts of other hardware for sale, just nothing I'm looking for. I'm pretty sure I can buy gift cards of lesser amounts, if you don't wish to take all $378 in one trade.
I don't have a number in mind, so just looking for the best offer.