If you want comparable performance from a high end AMD-based card, you have two options. Either stick two chips on one board for instant Crossfire mode, like the Radeon HD 5970, or overclock the hell out of a hand-picked HD 5870.
Gigabyte's Super Overclock HD 5870 is, as the name suggests, an example of the latter method. With a clear 100MHz, or 11.7%, added onto the core speed of a stock Radeon HD 5870, this is an ambitious card with ideas way above its station.
An elegant set of heatpipes helps to keep it cool at these extreme speeds, and if you want to push it further, there's a set of volt reading contact points on the PCB for the compulsive tweaker.
It had better deliver on its promise, though, since it costs the same price as the GTX 480 it hopes to unseat.