HD 5850 is faster than the GTX 285 (10.5") and measures only 9.5"
HD 5700 series which is as fast as or faster than the previous HD 4800s/GTX 260 measures only 8.5", shorter than the HD 4800 series (9"-9.5") and a hell of a lot shorter than the 260 (10.5").
the stock design dosnt look to bad for cooling as long as ur case has good air flow internally, those type fans usually just dump hot air into your case.