hp pavilion elite hpe-185a best gpu

hi all im new here and i just bought a hp pavilion elite hpe-185a. heres the specs
http://h10025.www1.hp.com/ewfrf/wc/...=es&docname=c02070138&product=4184711&lang=es
i would like to play ffxiv but i think i need anougher graphics card can anyone tell me the best card i can get with this desktop
and is the gt 230 bad or an alright card... thanks in advance

ive was looking at the 5850 but was rudely told i shouldnt have brought a hp the cards too big and that it will blow up my computer so thats when i came here. he didnt give me any other suggestion... i also have been looking at the 4890. chip size is smaller but ive never done an upgrade before so i need help