a 2500K is capable of handling a lot more than that. a 6970 or more.
If u r not fixed on what ur going to do invest in a better video card like a 6850 or better.
But what is ur resolution tho?? We need to know the resolution to make better recommendations.
By the way if u r planning to get another new 5770 anyway its better to get the newer 6770 priced almost similar and it goes well with ur old card. And it adds newer tech. They are perfectly compatible with each other just in case u r wondering.