Building new rig & need advice.

If you can, I'd return the board and DDR3 memory, nvidia boards are of subpar quality and only real advantage was that you could setup a SLI configuration (Which was a real plus... when nvidia was on top). DDR3 is still to expensive to be worth it, you won't see any performance benefits over DDR2, and you'll benefit a lot more from having 4GB of ram.

If you can do what I stated above, then I'd get an X38 motherboard, an HD 4870 or HD 4870 X2 (depending on your budget), 4GB of DDR2 1066 memory, and at least 640GB HDD from western digital.

If it's not possible, then I'd get a GTX 260 or a pair of them depending on the budget (Not the 216 core junk, you'd be basically paying +$50 per card, just for a 5% performance boost). You can get any nvidia card regardless of manufacturer and they will run all the same, it doesn't have to be an XFX card.

I am against nvidia-based motherboards (however not against the graphics cards), but it's still looking like a solid system. I hope you don't run into any nagging issues with it like many others have, I'd read some about RAID issues on nvidia based boards in case you're planning on setting up an array, otherwise good luck.