i'd get either, although to let you know the x800 wll use more power and use an external 6 pin pcie power plug. The7600gt does not, the 7600gt is also newer btw...
as prozac said though they both perform similarly, although the x800 doesn't support ShaderModel 3.0, if that matters to you.
your choice, they both perfom much the same, THG did a 'review' (well a review on quite a couple of graphics cards) about thegraphics cards in that price range recently
you cn also chck the interactive GPU charts on the THG homepage.