Santano, check the benchmarks of graphic cards/memory/cpu's and you will see where your computer is(tomshardware, anandtech, extremetech...google for them). one thing that you should keep on mind is that the benchmarks are done with computers in almost perfect conditions (fresh installed windows, minimum processes runing in OS that is, they dont install 30 different applications that will have process runing like mouse drivers or office or anything..., best power supplys, best wirings and heatsinks,
when they test cpu, you have best memory with insane low latency and top video card and superfast HDD, so the benchmark result relies only on CPU..) your computer will never be in that condition and get that.
when u check those banchmarks, you will get close idea where your computer is. and then decide if more $ is just for that much percentage of frames you can get.
if your upgrading just for BF2, than I would start with more memory, I would go with gaming grade ones that have low latency and make it 2 gigs. you check the timings rate like 3:3:3:8 and in general the lower are numbers, its better.
you want something that will work with your motherboard (check the mobo specs what it supports. like manufacturer and rating like DDR333 or DDR400...
second one would be the graphic card...you can go just as high as you are ready to spend. remember that card that costs twice more than other one doesnt mean that will give you twice more performance
I just want to say that the computer that you have is very good for more than 90% of all games and apps that are out there, but theres better if you have $ for it. and even if you spend $5000, you will still die if you come in SF server
