I don't mind if its 3 slots. Just can't be more than 3. Preferable less, because if it is exactly 3, airflow may be restricted due to my GTS250 working as a Physx card, which I intend on keeping. I haven't gotten to trying CPU Physx, but as I have just overclocked to 4.4GHz on my 2500K, I might give it a shot.
Any other suggestions would be appreciated, but this cooler would match the fans that are in my case.
EDIT: The cooler cannot be over 9" or a little more in length
I just got mine to run at 900 stable, which I am happy about. I'm going to leave it there for a bit at least. I don't know how those people get much higher scores than that with similar systems in terms of the 460 fan club, but oh well.
The cooler will work but you will run into the same problem that I had with my gigabyte 460. There will be some back pressure behind the cooler and some of the exhaust will loop back into the fans so having a fan near by is important. Beyond that you already figured everything out.