i have a great computer just want to know what which hardware would be most valuable to add on or replace

system:

dell workstation
2gb ram
200gb hard drive
2 quad core cpu 3.2ghz
nvidia quad vid card

i know its not exactly made for gaming but i use it for work just as much but would like it to be suped for gaming too

i would think more ram, what do you all think? maybe a bit more space on my hard drive

i play mostly online games FPS - half life deathmatch 2 and soon to play crysis...