I have a T-Bird 900, and I use the Taisol CGK747092 cooler. With the stock fan, I was running the CPU at 1 GHz. I then bought a Delta 7k RPM fan, too see how far I could push the T-Bird. I didn't realize just HOW noisy this thing is. I could get the CPU up to 1.1 GHz and it was stable enough to run benchmarks. However, it was not stable enough to run like that all the time, since games sometimes quit to the desktop or threw weird erorr messages at me.
I could however run it at 1050 MHz with the Delta, and it was 100% stable. But the the noise...that horrible, high pitched whine from the Delta fan was not worth it for 50 MHz. Turning the computer off, or just putting it into suspend mode (most fans stop when it enters suspend mode, including CPU fan) was a great relief. I have now put the stock fan back, and it's so quiet it's almost scary. I get quite high CPU temps, up to 47C under full load (also remember that the temp sensor on the A7V displays quite high values), but it's stable at 1 GHz. I wouldn't accept the noise of the 7k RPM delta fan even for 200 MHz. 300 MHz? Maybe... However, I'm going to buy a slightly less powerful, and also more quiet fan to replace the stock fan with. I'm sure it doesn't take a Delta 7k RPM fan to get the CPU up to 1050 MHz reliably. I'm also thinking about buying one of those cool things that allows you to mount a 80mm fan on the CPU heatsink.
My computer is still a bit noisy, since I have two powerful 80mm fans and a slotfan in there, as well as some other goodies. I can take that, though. It doesn't bother me at all. In fact, I like it better when the computer makes some noise, it sounds "cosy"
The sound of air flowing through the case is much easier on the ears than the high pitched noise from that overpowered Delta.