You have a 4890 on that CPU? You are CPU bottlenecked heavily.
That GPU is still good, you don't really need a new one.
Upgrading to a 2500k/DDR3, or 975BE/DDR3. You would get more out of going with a 2500K, but its totally up to you.
You could also wait till the new Bulldozer AMD CPUs come out as they are right around the corner.
Its up to you, but you don't need a GPU upgrade as much as you do a CPU upgrade.