Very thorough writeup of the GeForceFX 5200 and FX 5200 Ultra over at GamePC.

With the new GeForceFX 5200 GPU's, Gainward has made a 180 degree turn in the face of what people think of the FX and made these products completely silent.. almost. As the low-end Pro/660 card runs with a completely passive heatsink, the fact that it's silent is no surprise. The higher-end Pro/760 card, with it's fairly large heatsink/fan unit is also silent most of the time as well, amazingly enough.