PowerColor's HD 4890 PCS can impress with great performance right out of the box.
* Graphics Engine - RADEON HD4890
* Video Memory - 1GB GDDR5
* Engine Clock - 950 MHz
* Memory Cloc - 1050MHz (4.2Gbps)
* Memory Interface - 256bit
* DirectX Support - 10.1
* Bus Standard - PCIE 2.0
Being from the PCS+ family of cards, the PowerColor PCS+ HD 4890 BF Edition comes factory-overclocked, boasting 950MHz at the core and 4200MHz DDR at the memory. Bearing in mind the reference clock speeds of 850MHz at the core and 3900MHz DDR at the memory, you'll come to realize that these are some formidable clock speeds.
Full Review here - http://www.hardwarezone.com/articles/view.php?id=2919&cid=3&pg=1