I've had good luck with NVidia chipsets on cards made by EVGA, Asus. 7300's and now 9600's.
The 9600 GSO I'm using now was incredibly discounted, and so for $50CAN I figure I got a good deal. I don't play games, but together with a 22" monitor, it plays HD well.
Others will be able to give more detail on cards but keep in mind to note the memory bandwidth and what type of memory is on the card. If a card is full length, will it block any SATA connections etc? Some fans are huge - and passive cooling can take up even more space. Power requirements can be heavy, too, even with cheaper cards.