Ok I think I found a solution:

Asus EAH4850 TOP/HTDI/512M, Radeon HD 4850

It's a slightly overclocked version of the reference model that's on the same level as the 9800GTX+ . But the greatest advantage is that it comes with another cooling system that is tested much cooler than the reference model (computerbase.de).

As it isn't really more expensive than comparable models I think I'll going to take this one.