Quote:
With a 1440x900 monitor, 5770 or 5750 are your best choice and you can keep your power supply too! If you prefer nVidia, the 9600GT is a great card and it's not very power hungry, just make sure its not one of the cheap DDR2 models.[/quote]
I just got a 9600GT, the "low power" model from Galaxy. I am very happy with its performance at 1440x900, and am running it on a very generic 300 watt power supply.
So if you power supply is weak, I would suggest an ATI 4670or 4770 or a 9600GT. Check the output of your power supply and whether it has an external six pin connector.
The 4770 and most 9600GTs require an external connector, while the 4670 does not.
These cards should all be cheap, but they would not support Dx11 of course.
If you are concerned about this, wait for the 57xx series or even the 56xx series from ATI, as suggested already.