The cards are pretty much the same in the 1gb range. Some overclock them more, some provide better warranty. Out of those Xfx provides the best warranty.
There is no difference in any of those cards except for the 512 and 1gb version and the warranty the manufactuer has on those cards. The resolution does not depend on the video card but your monitor, check your monitor to see what resolution it supports up to and you'll find out your answer.
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