Upgrade, please help!

Hello, I'm thinking of to upgrade my system a little, my current system is :

Intel Pentium Dual-Core E5200 2.5ghz @ 3.25ghz(oc)
2gb ddr2 ram
hd4850 512mb
22"(resolution : 1680x1050)
asus p5kpl/1600 motherboard(pci express 1.1 x16)

im on a budget and the options ive chosen is these :
either upgrade to Intel core 2 quad 2.83ghz Q9550
or
upgrade the graphics card to hd4890 and get 2gb more ram(using xp so it can only see 3.5gb)
i mostly do lots of stuff at the same time and the oc of my current cpu did a huge improvement, 8 fps extra in far cry 2 and better response time,
i mainly do heavy tasks like coding and extracting huge files but i also play lots of games, the games i play is far cry 2, crysis, need for speed shift, grid, also source based games like css and tf2,

i need your advice, please tell me what upgrade i should do, thanks is advance