GTS 250 is a fine card, but it won't last much longer before it needs to be upgraded.
Currently, I'm using the game "Shattered Horizon" as the benchmark for current cards, meaning if your video card can run that game well, it will do great on virtually any game. I have a 9800 GTX+ which is virtually identical to the GTS 250, and as of right now, the 9800 GTX+ doesn't run Shattered Horizon very well. My resolution has to be turned way down and the details set to medium to medium-low. I thought upgrading my processor to a Quad Core might help, but it did very little to help with the playability of the game. However, newer cards, like the GTX 260 and newer ATI cards seem to have no problem playing this game. My fiance's HD 4870 512mb seems to run this game very well, and it's only about 30% faster overall.
Honestly, if you can manage it, I would get something more powerful. Otherwise, it will tie you over.