X58B-A or DX58SO?

Im building my new computer and i have to decide between X58B-A or a DX58SO, I know the DX is better but what are the main differences?

My new pc will have:

Radeon HD 5870 1GB Video card
i7 930 2.88ghz
8GB Ram
500gb harddrive
Windows 7 Home Premium 64 bit

With those specs, which one do you recommend and why? The price difference between them is $100-120 bucks where i live.

Thanks for you help

i meant 6 gb not 8(depending on board)