Passive WITH performance isn't easy. If I had to do it, I'd grab a 5850 and get a Thermalright Spitfire w/ VRM-R5, but it isn't cheap and it's rather bulky (TWSS).
If you want "really damned quiet" you could grab something similar my setup. Maybe get a reference 5850 and mod it with a Thermalright TRad-2, 1100RPM 120mm Gentle Typhoon, and VRM-R4. Way less noise than the stock cooler (I can't hear mine at all) and it performs better to boot. It would handle 25x16 gaming without many compromises.