depending on budget and preferred brand...
if its just for watching dvds n such then just get something cheap like a radeon 9600xt or a 9800pro...
if ur wanting to game..and got a mid budget, get an nvidia 6600GT...
if uve got quite a bit of money.. go for a 6800GT, 6800Ultra.. if ur more of an ati person, im not here to sway u either way, look into the x800xt and upwards.. for a good ati card from the x series, its going to cost u.
Imo, the 6600GT is great, price is good and performance is great.. the equivalent ati card to the 6600GT is nothing,
hope this helped, if u can post the money u want to spend, im sure there is the possibility for further assistance
Sig reinstated. SigSanta