Really the stock HD3870 X2 cooler is about the best dual slotted solution you can get (or so I'm told). Even 3+ slotted solutions I'm drawing a blank. The only HD3870X2 aftermarket cooling solution I can think of is the sick EK block.
plan on getting an HD4870X2 + EK block for that, and a Q9450 and a 2 stick 2 gig kit for x-mas this year.