IIRC a 6850 is just a rebadge of the 5850, except it uses less power, it might not overclock as well and may have a few less shaders from what I've read, it should still be almost as good as a 5850 for mining though...
but it's not) according to the hardware compare table... in fact 6850 looks like slower than 5830)
yeah, just saw that, I guess what I read was wrong, the amount of shaders on that card is pitiful...lol, the problem is that 5850s are hard to find for a decent price right now (at least here in the states), the 5830 is cheap and performs well, but it's a power hog, if you're gonna use that much powah you might as well spend the extra, get a 5870 and almost double your MH/s too...