I would recommend either the Noctua NH-D14 or the Thermaltake Frio which goes for $90 and $65 respectively. Both offer very good performance although naturally the Noctua cools better but not by too much if only 1 degree but it is much softer comapred to the Thermaltake cooler.
The Cooler Master V8 is really nice. A lot of people seem to not like it, but its a great cooler. I have a stock speed Intel Core i7 920 D0. In the winter the Ambient Temp inside the house is around 18-20C and my i7 idles at 25C. During summer temps are about 23.5C and the i7 idles at around 28-30C. This is using Artic Silver 5 thermal paste and the haf 932 case. Case makes a difference in your cpu, because case fans can help ventilate the metal heatsink, not just the fan that is inside it.
I sold it to my mate who was interested in getting a gaming computer and i was out of the country for a few months so instead of going to buy all the parts for him (which he couldn't wait for me to get back to do) i just sold him my computer and built one when i got back so it was a win win.
As mentioned (i think) my case is a HAF 932 so it has pretty decent cooling.
Also might as well through it out here, im experiencing some high pitched constant squeaking coming from computer. I have changed the motherboard and tried replacing the gpu's with no prevail. Have ruled it out to PSU or CPU fan. Wont be able to tell for sure until i have replaced cpu fan so hence, why i am getting opinions.
IMO it seems to be the PSU.
I also looked at the Cooler-master V8 but this was when i was considering what to use on my previous CPU and i found the Zigmatek dark knight to be cooler and quieter.
OK! I Really think that the V8 is terrible for anything above 3.8, to be honest at full load (prime95), Although it actually does keep my 3.7 955 cool at idle like blackhawk said, When you go full load its hot. But your best bet if you plan on getting it to 4.0ghz or 3.9 ghz is to get the Thermalright Venomous-X first suggested.
Here's some benchmarks on the Venomous-X, btw it beats the Prolimatech Megahalems, AND if you do get the Venomous-X remember to buy two high CFM fans for push-pull configuration for the best results.