Airmantharp probably wanted to say "that specific flavor of the 4870..."
I mean to say every specific flavor that does not fully exhaust out, meaning that it doesn't throw any air used for cooling back into the case by design. A quick check through Newegg or anywhere else will reveal a total of two flavors that satisfy those requirements, those being cards equipped with the stock AMD cooler and those equipped with the ICEQ4 HSF. I disqualify the ICEQ4 flavor based on complaints of it being loud, which you do not see on ones using the stock cooler. Thus, to satisfy the requirement that the cooler on the card be both quiet and exhaust the excessive amount of heat it produces out of the case, I can only recommend AMD 4870 based products that have the stock cooler; that's the only thing that I would put in my case. I will also point out, as I mentioned above, that the venting doesn't matter if you have a case that does the venting for you, and if so you probably don't care about noise, but maybe you do. My post is simply to inform the OP of the options available, and the consequences of various decisions.
Personally, when it came down for me to make a similar purchase, I wound up going with the GTX260. And even without considering all of the reasons to pick Nvidia, not that they all apply, the fact remains that getting equivalent total performance from an AMD product right now costs $60 more. I can't see how that would be overlooked, that's the price of good