Jimmy, if you're confident enough to take a motherboard out of a case and you're in a position to reuse your existing hard drives/DVD you could move to a Sandybridge based setup for under 400 quid.
The spec jarmstro came up with is very good, but a fair bit OTT. The i7 offers very little over an i5 in the RW world, but comes with a price tag of around £80 more than the i5. Z68 motherboards are very feature packed, but do you need Intel RST?, is SATA 6GB/s on your wish list?, SLI and X-Fire of interest?, ---if not consider the H61, about half ther price of a Z68 board.
16 GB of RAM?...a joke surely?....4GB is enough for
today, 8GB is being ready for anything in the next 3 or 4 years. When we get to the point that we'll need 16GB of RAM we'll be replacing our CPUs too.
Could you fill 2 Terrabytes of disc space Jimmy?...
The graphics card is OK though
All this is rather moot though if you're having to save for a while, because when you have the money you'll find the technology has jumped ahead again so any recomendations you'll get today won't be valid---best to save 3 or 400 and then see whats available.
Why the need to run the game with everything on highest settings?... the settings are only valid when compared relative to each other....
consider this:
you buy game 'A' and can run it with everything on highest
a week later you buy game 'B' but can only use medium settings
has your PC suddenly deteriorated?
no!...game 'B' probably has medium settings that are the equal of game 'A's highest settings.
The question should be "What spec PC do I need to run RW with acceptable performance and have good quality graphics with smooth game play"