-That's a slower HD, most prople recommend something like a Samsung Spinpoint F3 500GB drive since it only has one platter and operates at a much higher performance.http://www.newegg.com/Product/Product.aspx?Item=N82E16822152181&Tpk=samsung%20f3%20500
-If you want a fancy motherboard (I'm assuming you are since you listed a 790FX in your theoretical build, and because you want crossfire) - then I recommend going with their newer 890FX boards that came out recently such as the ASRock 890FX:http://www.newegg.com/Product/Product.aspx?Item=N82E16813157196&cm_re=890fx-_-13-157-196-_-Product
[If you don't like ASRock, there are other brands that have 890FX boards as well].
-If you don't want crossfire, and want a cheaper motherboard, then look at the AMD 770 boards:http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&Description=amd%20770&bop=And&Order=PRICE&PageSize=100
-If you insist on CrossFire, get two 4850 1GB cards in crossfire for $220. This CF setup generally performs at or above a 5850. Those 890 mobos will be great for CF as well. Otherwise the build looks good.
[You could also get 2 4870's for $300, or 2 4890's for $400].