Newbie looking for new comp help

[Undoubtedly]

Hello, I have raised myself some money in order to buy a new computer.
These are my current specs.
Intel(R) Core(TM)2 Duo CPU E8400 @ 3.00GHz (2 CPUs)
Card name: ATI Radeon HD 3870 X2
4 gig of ram

Now I only use my computer for playing games and watching videos.
Main games I play are Modern Warfare, World of Warcraft and soon to be Starcraft 2.
I'd love my computer to be able to play these games on full ultra setting and well enjoy the game to the best that this computer will allow.
Basically looking for a really good system that will be "great" for the next few years.
I have about $2000 AUS to spend, I current have a 22 inch monitor and mouse, keyboard and such, so I will just need a case full of goodies.
I don't understand all the details but if someone could help me well this would be very great for me.
Thanks for all and any time.
Undoubtedly.

 

[fastdude]

Full system specs please? I would drop the LGA 775 CPU, go for an AM3 setup, or even 1156, you'll have a hard time upgrading a dying socket. The 3000 series GPU's have been good, but are now outdated and I would get at least a 4000 series GPU. Personally I would go with a 5770. Although with your budget, you could probably stretch to a GTX460.

NOTE your budget is about £1200, or $1800 USD - will this include OS/monitor/peripherals? You were rather vague