Actually the gecube cooler is different for this card since it is a completley different board. its alot shorter than the reference HD3870 X2. one easy mod for this is to take of the plasic shield and take of the heatsinks and apply AS 5, then rotate the heat sinks so that the fins are running perpendicular to the length of the card.. and you can insert ziptie clips inbetween the back bracket to add more pressure. then you can adapt fans to each of the heatsinks and you can even make a bracket for the fans so you get the same look as the asus one.
http://forums.ebuyer.com/showthread.php?p=317109
i will post pictures and a guide on how to do it when i get my second one.
the zipties trick alone decreases temps down a full 3 degrees.
then when added artic silver 5 it dropped another 5 derees
but when i saw this guy on the link above i just had the perfect idea.
so i copied him and added two 92mm artic cooling fans and it dropped my temps another 9 degrees
but after a while my full load temps went down from the stock 80 and above to 53 on full load with stock voltages
but over clocked i was able to keep it under 65 no problem.
the only draw back is the fact that it can take upto three slots so this means when i get my second card and perform the same mod it will be almost touching my powersupply.