Why dont you save up for a bigger+better build later on?
DDR3 is still to become mainstream, new quadcores based on wolfdales will be released shortly, new chipsets, and not to mention the whole new architecture that is Nehalem which will be available on 4th quarter of 2008. Save money and buy a nehalem system when they first come out. At least you will have something to brag about, not to mention cutting edge at that time.
And if you want to buy now, you should buy an X38 or an 780i based motherboard, at least to have PCI-E 2.0 for fututre graphics card updates. Go for the Quad as well, it should end up being more future proof compared to a dual core IMO. 2x2 GB of RAM for 4 Total and a future expansion to 8GB.