This smells strongly of an eBay "escrow" service type of deal. If he's going to demand that you pay through escrow, then make sure YOU choose the escrow service. He may point you to a service "he uses", but in reality it'll be a website he (or a chum) owns that looks real, but in fact he'll drain your money leaving you with no car.

An S2K for 10G sounds way worth it, care to trade me my I-4 Accord for it? I'm not trying to be a dick here, I'm just saying it sounds wayyyy fishey.