Bear in mind that you're only really going to need something in the 30-40 FPS area (on super high settings) to make your game smoothly playable. A Phenom II X4 with a 5850 could reasonably be expected to do that for 2 years at 1920x1080, with maybe a drop to "just" high settings for the third year before your next upgrade. Talk of 6950/70s and GTX 570s is mad overspend, even at that resolution, and as the OP's screen is only 21 inches, I'm guessing it may only be 1680x1050.
id go i5 over i7 atm
+1.
Phenom II X4 system will do all you want easily, add a HD5850 into the equation and problem solved - if you spent £240 on graphics you could get a HD6950 and flash it to a HD6970 - 3rd fastest card on the planet and much faster than the over-priced Fermi GTX570.
H70 is not particularly good for this price either, its a bit naff
A decent air cooler just as an Akasa Venom will do the same job for £30 less.
Your specs are fine op. Maybe a 6950 for the 570. The way i see things, you might as well get the best you can afford. None of this phenom or 5850 nonsense especially as you will be playing crysis 2.
Get the HX corsair for modular goodness ?
MW
That's the amount you're paying extra to run Crysis 2 on super-high instead of high. You can get a system for £700 instead of £1200 that will perform *near identical*.