I've just picked up another 5870, and well the fan on 1 is loud enough for the both of them! I went ahead and got 2 aftermarket coolers for them and I was wondering if anyone else has had good luck with these or any other for the 5800 series
XFX 5870(Non Ref)
ZEROtherm CoolMaxx 3000 http://www.newegg.com/Product/Product.aspx?Item=N82E16835887024
The board on the 5800 series as far as coolers go, is the exact same layout as the 4800 series, So it'll work fine, Someone else has posted stating it works on their 5850 which again is the same layout as the 5870...