MSI is workign hard to finish its overclocked Radeon HD 2600XT with 512 MB and a massive dual slot cooler. The card will end up working at 850 MHz core and 2300 MHz memory and aims to be among the fasest cards around.
The card is called MSI RX2600XT Diamond 512, Radeon HD 2600 XT, 512MB GDDR4, 2x DVI, TV-out, PCIe (V098-020R) and the sources close to company have confirmed that the card will be available in September.
Just like any HD 2600XT it has UVD and HDMI over DVI
You can preorder one here.