It's apparent that the HD4800 series runs way hot. I need to cool the HD4870. I'm not interested in overclocking, I just want an ice cool case, just because when hardware runs cool, it lasts longer. Are there any <$30 coolers that could drop the temps below 75ºC at full load?

4870, unlike 4850, already use dual slot stock cooler. A cheap $30 aftermarket cooler is unlikely to cool it significantly better the the stock one. Besides, if you don't mount it properly, it'll be worse. Might as well just bump up fan speed instead.

i dont think there is a aftermarket cooler for them two yet. but no doubt those are hotter then 9800GX2 suprisingly!lol

According to reviews, whatever worked for the HD 3000 series works for the HD 4000 series.

^^^ OrlY???
Nice, cos the 4850 sits at about 80c load from my initial tests.

http://www.hardwarecanucks.com/for [...] ew-21.html
 
"This little exercise has made it apparent that provided it has the proper amount of ramsinks and VRM sinks, ANY cooler compatible with the HD3870 series will also be compatible with the HD4870 and HD4850. We tried the Thermalright HR-03 GT, Thermaltake DuOrb, Coolink GFXChilla and Arctic Cooling S1 Rev.2 and every one of them fit without any problems at all. Beautiful, isn’t it?"

http://www.arctic-cooling.com/vga2.php?idx=166
works with the 4870