In terms of single GPU performance, the Radeon HD4870 set the bar pretty high, and the Sapphire Toxic Radeon HD4870 512MB graphics card had its work cut out for it to do much better. With a factory overclock of 30MHz on the GPU and 100MHz on the memory, the Toxic version generally did perform better, but not always by much.

http://www.bigbruin.com/2008/toxic4870_1