I'm not surprised that the HR-03 GT cooler is the best cooler for the 4870. However, I thought that Thermalright's new T-Rad thingy would be revolutionary yet it gets beaten by the low-quality and cheap S1 Rev. 2 cooler. What an embarrassment!
I'm running my 4870 stock heatsink at 25% which results in a load of about 70 degrees at 790/4000. I can't go higher until I flash this card. Once that happens of course I'll need one of these aftermarket heatsinks to go along with it...
I had the S1 Rev. 2 on a 4850 card over the summer. That cooler works well but it's such a cheap piece of $hit in terms of build quality.