Originally Posted by
Webby
If you want to do a bit of a comparision your 2900XT is on a par with a 3870 so you will see decent improvements in applible image quailty settings and/or frame rates by moving to any cad from the 4850 and above.
Crossfire has moved on a bit and the current crop of cards crossfire very well you could consider 2x 4830's in crossfire (£180) they will obliterate a 4870 or GTX260 in most things.
As Cat says the newer revisions are coming soon so if you can wait it could be worth it either to get the newest tech or to catch a bargain as the old stock prices fall.