Keep in mind that you'll have to meet the Power Supply Requirements for whichever video card you choose. It's IMPERATIVE that you know what power supply your friend has. What you'll need to know is:
Total Amperage across the 12v rails
What/how many PCI-Express connectors are available. There are 6 pin and 8 pin connectors, you'll need to take inventory of these as certain video cards will need different ones. The video card specs on Newegg will detail what power connectors it takes.
These can be found on the white sticker on the power supply itself. It may take you taking the case off and using a flashlight to see it, but you have to know. If your power supply isn't powerful enough, it won't run the card properly, or even at all!
I'm thinking waiting on Barts Pro and XT to come out. That will definatly result in a few price changes. So... Before you buy any of those cards. Nvidia just doesn't have the ability to counter ATI right now so you'll expect to see the GTX 460 (as said before) drop in price. That will lead to the ATI counter, why as a result drop the price of the 5770. But all speculation, I agree with the 460>5770>260 evaluation.