I'm currently running a GTX275 on the same SB setup as you, which is very similar performance to the GTX280 (darn site quieter tho!).
It's not worth upgrading to anything less than a GTX560 or 6950 IMO. The 460 barely offers any improvement at all, although it would give you lower temps, noise & power consumption plus DX11.
I was looking at the 570 but was waiting until the 560 arrived to see how it compares. I've now pre-ordered a Gigabyte GTX560 Super OC which will hopefully arrive sometime next week. Reckon I'm looking at about double the frames over my current 275.
It's not worth upgrading to anything less than a GTX560 or 6950 IMO. The 460 barely offers any improvement at all, although it would give you lower temps, noise & power consumption plus DX11.
I was looking at the 570 but was waiting until the 560 arrived to see how it compares. I've now pre-ordered a Gigabyte GTX560 Super OC which will hopefully arrive sometime next week. Reckon I'm looking at about double the frames over my current 275.