techPowerUp posted a review on the Sapphire Radeon HD 4850 X2 2048 MB video card

Being priced at reasonable $419, the Sapphire HD 4850 X2 is designed to take some market share from NVIDIA's GTX 280. The card features 2 GB of GDDR3 memory and comes with a custom designed cooling solution. Even though you would expect very little overclocking from a dual-GPU card, we saw an amazing 15% performance increase from overclocking without touching any fan settings.

Sapphire Radeon HD 4850 X2 2048 MB Review