The Biostars are proven overclocking champs when it comes to the AMD platform.  Price/Performance, you can't really go wrong.  Asus generally are fairly solid boards too, and I personally have a Gigabyte board.
Honestly though - since you have a GTX260, you should be looking at a 790FX+SB750 board instead of a 790GX.  The 790GX has video built in, which will be useless to you.  Also, you may want to wait about a month for the AM3 boards and chips to come out since you're making a platform change anyway.  You'll likely get a bit more performance out of it for just about the same money (once RAM prices come down).