A 5970 is really for large monitors, somewhere above 1920x1080. It's been mentioned before but a 5970 is 2 5870's slightly underclocked and put in crossfire mode all in the same card. you probably wouldn't notice much difference at 1680x1050 between that and a single 5870. The thing I've noticed when running SLI (not sure if the case is the same for crossfire but I believe they use similar techniques) is that I get the most noticable difference in a game when resolution is a factor. For instance if a game runs smooth at 1440x720 but not at 1680x1050 then adding a second card in SLI will give me the extra grunt I need to run it smoothly at 1680. But if it already runs smoothly at 1680 then I don't notice much difference with the second card, especially with vsync enabled. I'd say if the 5970 is nearly as cheap as a 5870 then go for it by all means but if not then i'd wait for the card above the 6870 to come out sometime early next year as it will provide the same grunt with better tesselation performance than the 5xxx series. Even the 6870 would be enough for your resolution and if your PSU can handle it you could keep your 275 for Physx.