Today Sapphire announced a slower version of the very popular X1950 Pro: the X1950 GT. Everything is the same between the Pro and GT with the exception of clock speeds.
The X1950 Pro runs at 575 MHz on the core and 690 MHz on the memory (1380 MHz effective). The GT takes things down a notch to 500 MHz on the core and just 600 MHz on the memory (1200 MHz effective). Given that these two cards use exactly the same core, adnt that the core is 80nm, I'm betting that the GT will be a very nice overclocker.
As always, for more information you can check out the card page for the X1950 GT.