Sapphire HD 5850 Toxic 2GB ships with a slightly tuned GPU frequency, 765MHz, while the larger memory buffer spins at a higher frequency as well, 4500MHz compared to the stock 4000MHz.
Sapphire has gone with the Vapor-X cooler for keeping temperatures on the right level. With HDMI, DVI and DisplayPort outputs there is Eyefinity support and the price tag is said to be a few tens above the 1GB model, perhaps around $300.