I recomment the GTX 460 1GB version. It has a higher cap on overclocking and scales better in SLI than the HD5830 does in Crossfire. The GTX 460 with a decent overclock usually better than the stock HD5850 in most benchmarks and even better than the stock HD5870 in a couple of instances. Two GTX 460's in SLI perform better than the HD5870 and the GTX 480 in most benchmarks.
GTX 460 is the top choice today if you want to buy a GPU without overpay. but everything change real quick. like one month ago 5850 is still our top choice.
in most review they compare GTX460 756M 675Hz with other card.
but from last week GTX 460 1M manufactured OC 800+Hz just hit market and it will beat 5850 in performance. keep in mind, some cheap 5850/5830 has no OC ability.
Not like 470/480. 460 consumes less power, create less heat and can be real quiet if you bought right one.