That's a single core. you could buy that and you might see pretty good improvement over whatever it is that you have. But honestly, its main purpose would be waiting for a new CPU/mobo/RAM
The value of the 5770 in particular is clearly not going to be in its performance. Compared to AMD’s 4870, it loses well more than it wins, and if we throw out Far Cry 2, it’s around 10% slower overall. It also spends most of its time losing to NVIDIA’s GTX 260, which unfortunately the 4870 didn’t have so much trouble with. AMD clearly has put themselves in to a hole with memory bandwidth, and the 5770 doesn’t have enough of it to reach the performance it needs to be at.
If you value solely performance in today’s games, we can’t recommend the 5770. Either the 4870 1GB or the GTX 260 would be the better buy. So here’s the bottom line for the 5770: Unless you absolutely need to take advantage of the lower power requirements of the 40nm process (e.g. you pay a ton for power) or you strongly believe that DirectX 11 will have a developer adoption rate faster than anything we’ve seen before for DirectX, the 1GB 4870 or GTX 260 is still the way to go.