Ditch the 5200+, get and E6600 instead, £10 more and considerably more powerful. Along with the E6600 you'll need a new mobo, the Asus P5B is about the same price as the K9N, its a pretty good mobo, and oc's fairly well. Everythign else looks good.
The Sharkoon Rebel 9's 250mm case fan is a bit noisey (more like a gust than an irritating noise). I use a fan controller to quieten down the fans and it works nice. Remember to buy either a 120 or 2 80mm fans for the rear exhaust as this doesn't come with em.
Cools everything nicely tho
The Corsair PSU I have too... brillaint (it's a Seasonic M12) and whisper quiet. Runs my 8800GTX perfectly though I wouldn't want to try SLI with it though. Why SLI when you've got a GTX anyway??