So I have about $500 to upgrade my gpu's with. I've got a 1920 by 1200 monitor, and may get a second one later on, and an i7 940, with 6 gigs of ram. My mobo supports crossfire or sli. Currently, I have sli 260's, 192 version.
Currently, I'm thinking sli 470's, or a 580, but not sure which to get, or if its even worth upgrading my gpu's.
SLI 470s would be a major improvement. I would say that is the best option for the money. You could go with a single 580 for less issues, but I'm pretty sure than sli 470s would far outpace a single 580.
I'd wait for the GTX 560. Two of those may end up being your best choice. Also I would be thinking about adding 2 more monitors for Nvidia Surround(or eyefinity.) Gaming on two monitors doesn't work so well except in specific games.
If your PSU is 1Kw then you should not have an issue with it, particularly if it is a good brand, unless you will be overclocking your CPU and graphics card. Which brand and model is it?
Whether or not it is worth upgrading is a personal decision. What are you not getting now that you want to get? With you system now you should be getting pretty good game play. Which card are you now thinking about upgrading to?