As one who had a 930, I would say that if you want to go anywhere near 4 gig get a good quality cooler. No disrespect to Dude but while the cooler listed is good, I'm not sure I would use it if I'm going for a 4gig OC.
This is really where you have to pay attention to reviews when looking at coolers. Example pay attention to what the OC speed was as well as the temps at load and idle. If the review fails to mention the load temps. chances the cooler isn't that good.
You might want to note the OC speed. Overclocking to 3.5 is a far cry from overclocking to 3.8 and above. This is where the heat really ramps up. Personally I'd do a lot of readings on CPU coolers to get an idea of what you want.
As a side note, be aware that there are a lot of things that go into overclocking, and not everyone takes these into consideration. For example, plenty of people will tell you they can overclock to the moon, what they won't tell you is that it isn't 24/7 stable. In short some just overclock for benchmarks, but for everyday use, they usually back down. This is where research and deciphering through the BS comes into play.
I have an old Q6600 that's been running overclocked (2.4 to 2.9) for 6 years with no issue. Overclocking can be fun, if done right.
BTW my i7-930 was overclocked from 2.8 to 3.5 using a
Noctua NH-C12P SE14. You can see my thoughts on it here:
http://www.sevenforums.com/hardware-devices/81169-experience-gigabyte-motherboards-3.html#post775794 (scroll up the page and you'll see a better pic).
Anyway that same cooler is now cooling an overclocked i7-950 from 3.06 to 3.80. it's been running that way for about 2 years now, if I want to go beyond 3.8, I'm going to need a better cooler.
My two cents.
Here is another one to look at. Reading through some reviews it works on OCed above 4.0.