Re: 4870 or 4870x2 and DDR3 or DDR2?
A 4870 would be just fine for that resolution even a 4850 would be good. Are you talking about literally two 4870s in crossfire? or the 4870X2 which is over $500? Either one would be waste for that resolution. Those are only needed for very large resolutions or dual monitors.
And DDR3 isn't totaly utilized yet, so it's better to go with DDR2 ram. Plus DDR2 is dirt cheap. Wait for DDR3 to see what it does when Nehalem comes out with the X58 boards.
Random movie quote to make you seem hip and "with it":
"Please take the chairs away. I don't like them. The big one is staring at me and that short one is being very droll."