I'm an old system builder, I have always advocated that one starts off looking for the best Mother Board they can for the money ... I have never recommended anyone gets a MB with on-board graphics.
I've had a quick look at your choice, I see you have chosen such a MB ... now, I would be suggesting something different, but I'm out of that game, I let the young one here usually do all that donkey work.
Thing is, it's obvious you missed that, or knew that the built-in graphics would not be that good for games ... however, if, as I suspect, you didn't realise it already has it's own graphics, then you don't have need for another ... you can of course, add a 9800GT with go-faster-stipes at a later date when money & need arises.
Food for though ...
TTFN