Though the CPU draw is typically second to the GPU, they are the two big power users in the system. I could suggest to you the example of my build, a 2500K and GTX 460. It is only something like 400W that's more technically required, but I wouldn't have gone with less than a 500W, but more inclined to have even a bit higher.
Probably one of the more important aspects that's overlooked would be the actual amount of that wattage to be delivered on the 12v rail. Check the amperage of said rail on the PSU, and multiply it by 12. That is how many watts the 12v sees, and is one of the reasons you can't really just say a wattage requirement. Again, it's depending on what GPU you're gonna be using, but something with more than 30a on the 12v would be a good minimum to shoot for.
You can also consider the efficientcy of the PSU. Something at least 80+ bronze certified would deliver the power better (less lost along the way). You may also want to consider a reliable brand, such as SeaSonic, Corsair or XFX.
OCing Sandy Bridge is simple, especially since there is no need to reduce one ratio to compensate a reference clock, or tweak RAM settings. When I first got mine, I literaly just started changing the CPU ratio. Got up to 4.5Ghz before I knew it.
There's no guarantee you'll be reaching 4.9Ghz with any cooler, especially if you're to keep your voltage sensible. One should only expect somewhere in the 4.0-4.5Ghz from a 2500K, and just be happy that more may be possible. Also, the use of AVX does increase temps, and decrease the OCing potential. Personally, I see no need for a better cooler than what I have (CM Hyper 212+), since the Vcore gets to the uncomfortable zone before temps.
But if you're really wanting a better cooler, I'd say consider a Noctua (NH-D14 comes to mind).