Any of the newer GTX 6xx series cards will do you well and the only problem I have with ATI is their drivers aren't the best and have historically performed poorly in comparison to the nvidia driver counter-parts. As for the 7xxx series ati cards, those are alright but if you have a budget for a nicer card, look at the Nvidia GTX 6** series.
Also get whatever video card you're going to buy from Microcenter with the extended warranty because you will be able to retain the value of what you spent on your card at the time of purchase 2 or 3 years down the road when you want to 'cash in' on your warranty. I.e. you spend $250 on a video card from Microcenter and get the warranty, fast forward 2 years and you take your video card back to Microcenter and say it's broken I need a new one and bam, you get a gift card for $250 towards WHATEVER you want.
I went from a $99 dollar video card up to a $500 dollar video card that way over the past years.