^^
well, get a gpu specifically for the core i7, forget abt ur olkd system dude, jus keep it for surfing net and other type of d/loads..
For the gpu (graphics card), here even at digit we hv 2 schools of thought..
1.) nVIDIA supporting members (incl. me) hence i wud recommend u a card but ONLY wen u say ur budget..

but the most favourable cards from nVIDA are gtx 260, gtx 280, gtx 285, gtx 295
2.) ATi supporting members (my rivals..lol..

) the favourable cards wud be 4850, 4870
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So post ur budget and i will post the config suitable for ur budget..

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Cheers n e-peace....