I'm using the Xigmatek HDT-SD964 in my first build. It does pretty well, but when the fan gets over 2200rpm I can here it over my other 4 case fans running on med. I normally keep the CPU fan at 1800rpms which I set in BIOS. I also set the fan target speed at 50C which translates into 54C in Core Temp. I've also mounted the heatsink horizontally so that the HS fan is blowing upwards towards my cases top exhaust fan.
I'm running a Q6600 and with an ambient temp of 22C, my idle temps were 36, 33, 26, 33 in Core Temp. This is also in an Antec P182 case and I probably could have done a better job at applying the TIM. When running prime95, I can keep my temps under 55C with the above fan setting in the BIOS but the longest I have ran prime is 2 hours at stock CPU speed. The fan does get very loud and often hits top speed when running prime.
I've OC'd my Q6600 to 3Ghz (344 x 9) with stock volts (VID 1.325) and the idle temps are basically the same. I can still keep the prime temps under 55C, but the longest I've ran prime95 is 4 hours. I've been dealing with other non-OC related problems lately.
This is a good cooler for those that don't plan to OC big and don't max out the CPU often. The SD964 can cool well, but the noise when maxing the CPU is annoying. With my current OC and fan settings, the only time I have heard the fan speed increase is when running prime95. The slightly older games I play (Battlefront, NFS Most Wanted) don't get my CPU above 48C with Core Temp which doesn't trigger the fan speed increase.