R600XT will be officially known as Radeon HD 2900 XT when it launches in May.
It seems that R600XT will be available first followed the XTX. According to

DailyTech
, the Radeon HD 2900 series features 320 stream processors and
supports 128-bit HDR rendering, 24xAA, physics processing. Other features
include integrated HDMI output capabilities with 5.1 surround sound. Although
the wait for R600 is unbearable but the consoling part is that R600XT stood up
well against NVIDIA GeForce 8800 series. Using a Core 2 Extreme QX6700
processor, R600XT scored 12K in 3DMark06, slightly better than a GeForce 8800
GTX. It is benched on the latest 8.361-RC4 drivers, quite an improvement over the older sets of drivers. The
core clock of R600XT stood at 750MHz while the memory is at 820MHz. It looks all
decent for a US$ 399 card.

R600XT will be officially known as Radeon HD 2900 XT when it launches in May.
It seems that R600XT will be available first followed the XTX. According to

DailyTech
, the Radeon HD 2900 series features 320 stream processors and
supports 128-bit HDR rendering, 24xAA, physics processing. Other features
include integrated HDMI output capabilities with 5.1 surround sound. Although
the wait for R600 is unbearable but the consoling part is that R600XT stood up
well against NVIDIA GeForce 8800 series. Using a Core 2 Extreme QX6700
processor, R600XT scored 12K in 3DMark06, slightly better than a GeForce 8800
GTX. It is benched on the latest 8.361-RC4 drivers, quite an improvement over the older sets of drivers. The core clock of R600XT stood at 750MHz while the memory is at 820MHz. It looks all decent for a US$ 399 card.p>