I highly recommend 2koolperformance . Great site and easy to deal with. Its a Canadian company so us Canadians dont have to worry about being screwed on duties. Also one of the few sites that accept online interac.
If you know what you're looking for, ebay's not a bad option... Haven't done any sled parts off there yet, but I've bought radio and computer equipment off there before. A lot of people don't have any clue about what they're selling, but if you know what you're looking at you can find some good deals there.