Looks like XTX are cherry picked cores and that's probably why ATi is charging $100 extra for them. I got the itch to OC the new XTX I bought last night and it clocks to 750/900 without breaking a sweat. I think I can easily push the core to 800 mhz or higher but want to wait until the AS5 settles in and my ramsinks arrive. The XT I had on the other hand was barely pushing 720 core and 840 memory before artifacting. I've been reading xtremesystems forums and with the exception of a few people, it seems the XTX cards do clock higher than the XT. So despite having the same ram, most of the XT's don't clock as well as the XTX do. I suppose if you are an overclocker, that extra $100 for the XTX may be worth it.