Do I need to upgrade?

[sativa]

I am playing Total War Empire and CoD5 atm on this spec which is over a year old:

Processor: E6750
Motherboard: Asus P5K
Memory: 4Gb OCZ PC2-5300
Graphics Card(s): MSI 3870X2
Hard Drive(s): 2 x Raptors
Sound Card: XFi
Case: Antec P182
Power Supply: Seasonic 530W

Happy to pay a fair bit for a complete overhaul but am I *really* going to notice many differences (I do get slow down on Empire with v.high settings).

I play at 1680 x 1050 on a Samsung 2232BW (22")

 

[sativa]

can go upto £500 plus sale value of other items.

More concerned whether i will *see* any benefit