Zip is correct, the Gigabyte board will not SLI/XFire. The board he suggested seems a good idea. If you don't care about USB/SATA III then the board he has linked is a great price and perfect for you.
For me, the only other choice for board which would also include USB/SATA III would be the Asus P7P55D E Pro. But that is $180http://www.newegg.com/Product/Product.aspx?Item=N82E16813131621&cm_re=asus_p7p55D_E_Pro-_-13-131-621-_-Product
So it is beyond your price range and likely not worth it to you if you don't need the latest tech.
Having said that, I would actually purchase a GTX460 1gb card instead of the 5850. The MSI card is only $205 after rebate which is a lot cheaper than the 5850 and is a good performing card. The main reason I recommend it though is because you plan on using a 2 card set up and due to SLI being superior for scaling, the GTX460s paired actually outperform the 5850s.
Currently my view is - for a single card build go 5850, but if you have a mobo to support SLI/Crossfire, then GTX 460 is a better way to go.
With the money saved you coul even go with the Asus P7P55D E Pro board if you really wanted to