Revamp of old build

Ok, so this originally was going to be a slight update to my old system, now it seems to be turning more into a completely new rig.

Any advice or recommendations greatly received.

Approximate Purchase Date: End of Feb

Budget Range: (e.g.: 600-800) £450

System Usage from Most to Least Important: gaming, surfing the internet, watching movies

Parts Not Required: keyboard, mouse, monitor, speakers, OS, HDD, SSD, optical

Preferred Website(s) for Parts: ebuyer.com

Country: (e.g.: India) UK

Parts Preferences: Intel CPU

Overclocking: Maybe

SLI or Crossfire: No

Monitor Resolution: 1920x1080


Ok, so far i am looking at the following:

Mobo:Asus P8Z68-V LX
CPU:Intel Core i5 2500k
RAM:Corsair Red vengeance 8gb 1600mhz
Case:Coolermaster HAF 912
Additional Cooling:Coolermaster megaflow 200m red LED fan
PSU: Wasnt too sure on this as ive been caught by bad supplies before. The one i have been looking at is the Antec 520w High current Gamer

Thanks in advance for any help you can provide.

Edit: Forget to mention, i currently am using a Radeon HD4850, i will be updating this in the near future to a HD6870, so any recommendations would need to be able to accomodate this.