I would recommend this one if you really want to spend all $300.http://www.newegg.com/Product/Product.aspx?Item=N82E16814143190&cm_re=gtx_285-_-14-143-190-_-Product
I don't really like the idea of buying two cards at the same time for SLI/Crossfire. If you spend some money now to get a very good single card, then you can spend even less later to get another one for SLI/Crossfire. Here's how I think about it:
Buy a single card that puts you in the top 10% as opposed to buying two cards that put you in the top 5%. When your cards get older, buy another of your original card to keep you in the top 10%, as opposed to those two cards you could've bought together before that are now down to the top 20%. Sure you could upgrade those but now your paying even more again. :P
Either way you should wait for the 5 series to lower some prices and then make your decision.