Upgrade-my-pc MTV

[Walkerie]

Hi guys , looking to upgrade my PC fairly soon currently own

64B AMD 3200+
1 GB DDR400 RAM
ASUS A8N-E
OCUK 7800GT
Hyper Type R 580W

would like to upgrade my pc with the upmost limit of 200 pounds

I know this isnt much but atm is all i can afford
and also if your going to specify 2 parts , could you specify which one would give the biggest performance increase out of the two. thanks

P.S im a gamer

 

[Walkerie]

and how much increase would this likely to give interms of performance?

 

[Walkerie]

BUMP with budget of 300 now.