KFA performs better than the 5850, sometimes on par with 470 or even 5870 and they have also solved the fan issues with a new BIOS
OF course, it costs more than the cheapest 5850, which can overclock WAY beyond the 460gtx performance, the KFA is preoverclocked, quite heavily with not much headroom in it, the 5850's are essentially heavily underclocked 5870's and have huge headroom, the only issue being voltmoddable ones are rarer. A stock 5850 spanks a stock 460gtx, and a overclocked 5850 spanks a overclocked 460gtx, paying more, for a much slower card pre-overclocked is daft.
There has NEVER, in over ten years, been a worthwhile good value pre-overclocked card. You can get a £187 460gtx 1gb and overclock it to the KFA's speed, why on earth is spending £30 more for identical performance, card, cooling etc, good, its not, thats almost a 20% premium for the same card with a different bios.
A 460gtx 1gb would be the card of choice, its noticably ahead of the 768mb version, the MSI looks like the best one to go for temps/noise wise, but price wise its starting to run very very close to 5850's which are just better cards. A stock one will overclock ok, not great though, but is a decent wedge faster, a highly overclockable one will run you a bit more cash unless you find a great deal somewhere, those should overclock a heck of a lot faster.
A cheaper 460gtx 1gb, or a 5850, stupidly expensive pre-overclocked 460's or 5850's, or any other cards, are simply never worth the premium.
A 5850 would let you run 3 screens off one card, but I really wouldn't want to be gaming at 3x1680x1050, or 3x1920x1200 with a single card anyway so not such a big deal. For 3 screen gaming I'd be looking towards 2x5850's or 2x460gtx's anyway, either setup should be fine for surround screen gaming.