On the graphics card, after doing some quick skimming, it appears the 4870 beats the 9800x2 on every game but Crysis by a good amount. So the 4870 will save you a bit of $$ and be better
May want to look into getting a motherboard that will support Crossfire. It should not be needed, but I would see what the price difference is that they have. if it is under $50 buy the crossfire motherboard. If it is more I would stick with a single GPU solution.