Ive had really good success with
http://www.boardzone.com. they are in canada but have fairly good prices. heres a tip for you if you can pull it off.
they have prices in both US and Canadian dollars. they ask you where you are from and give you the corresponding prices for where you are. but their conversion isnt as good as market price for the exchange. I have ordered from them 3 times and 2 out of the three times I convinced the guy I was ordering from to charge me the price in canadian dollars instead of the US price. I told him even though I lived in the US I wanted him to charge me the canadian price in canadian dollars to my credit card. Your credit card company will often give you a much better exchange rate than what they give you and save you just a tad more money.
actually its not really true, I only got them to do it correctly once. the second time he converted the canadian to US on a calculator and gave me that in US dollars, but it was still cheaper than the regular US price.
either way it took a lot of talking and a lot of explaining. they may or may not go for it. but if they do its great for you. good luck.