I wouldn't say that all the powered by ati versions are a bad choice, some of them are actually better in the cooling department than the actual ati version. Tom's hardware did a review of some of the powered by versions back in Nov. that can be found here:
http://www.tomshardware.com/graphic/20021104/index.html
Sapphire cards are usually good, they are the main partner with Ati, although I'm don't know what kind of warrenty you get with some of the "other" cards...3 years for a retail ati version.
Just my two pennies.