There will be at least two versions of RV630 card. They will be covered under the Radeon HD 2600XT brand. The biggest difference between these two XT cards will be the memory as the chip can handle GDDR 3 or GDDR4. DDR2 is left for slower chips.
The new chip is 65 nanometre, supports DirectX 10, HD Audio, HDMI, 1080P HD playback. We still don't know about the clock speed of this chip but it might be even faster than 800 MHz.
The funny thing is that some overclocked versions of the cards can handle even GDDR 4 but the bad side of the story is that the memory interface is still 128 bit only.