PLS dun get 5000 series cards or any PCI 2.1 cards,
although some acticle said is backward compatible,
but i tried to install 5750 on D915gev, it cant work.
i install 4870 and 9800gtx+, both of the card run well for me
P4 3.0 HT Presscott
4G DDR2 800
1TB seagate 7200.12 (win 7 64)
80G maxtor (win xp pro sp3 32bit)
U can try to get 4870, if u got the budget, or 4770,
i think both of this card are great for u.
what kind of ur power supply u use also important,
maybe post ur PSU model, let people check for u