The case that cools modern GPUs the best is the Silverstone FT02/RV02 with the new AP181 fans. No case outperforms the Silverstone FT02/RV02 with air cooling.
http://www.newegg.com/Product/Product.aspx?Item=N82E16811163154&Tpk=rv02
http://www.newegg.com/Product/Product.aspx?Item=N82E16811163161&cm_re=ft02-_-11-163-161-_-Product
Silverstone build quality is some of the best, only surpassed by Lian Li. The cable management in these cases is quite good, and they are actually really easy to build in.
I purchased a Silver FT02, because its a beautiful case and it's cooling is amazing. I can tell you that I haven't been disappointed with anything about this case.
Here is a review of the special addition FT02:
http://www.bit-tech.net/hardware/cases/2010/08/12/silverstone-ft02r-w-review/1
Note that it actually comes with the new AP181 fans (demo:
http://www.youtube.com/watch?v=8m8fC809TK0 ). The RV02 now comes with these fans too, and will perform exactly the same. Note that with hotter running cards, like the GTX 480, the FT02 really shines. In that review it was very close to the HAF-X, however I've seen people get a 10c drop in temperatures switching from a HAF-X to an FT02 with GTX 480s.