check the price and availability of the following cards, ask around the shops if you can:
6670 1 gb gddr5
5670 1 gb gddr5
5770/6770 1 gb gddr5
6750 1 gb gddr5
gts 450 1 gb gddr5
gddr5 is important because it's fast enough to handle powerful gpus all the way to the high end. ddr3, gddr3 are slower. imo the 5770/6770 (if your power supply can support it) is the best among the ones listed followed by 6750, gts 450 and 6670.
for 1280x1024 or 1280x720 the cards above would be fine.