XFX factory overclocks their cards, they also come with a double lifetime warranty. The overclock difference isnt that much, so if its cheaper get it. But I wouldnt pay extra for it.
The core is clocked at 590 mhz vs the normal 560 mhz, the RAM 1600 Mhz vs the normal 1400 mhz.
Bigsaucybob, its the cheapest 7600GT after MIR, tied with the eVGA. If I were you, I would consider the eVGA card because it has a much better warenty.
its not worth it if you're going to overclock it yourself, but by all means get the card and get gaming!
personally id either get the o/ced one... but i like my 7800gt lol..