I believe you're asking the wrong question.
If you want a new GPU you should start be enumerating the following points:
- what game you want to play
- at what resolution
- you'll play with a CRT, a plasma or a LCD?
- how much eye candy do you want
- if you're willing to reduce resolution to increase eye candy or the opposite
- what system do you have (motherboard, cpu, ram, power supply)
- how much are you willing to spend
After this you can ask "what card should i buy?"