There is lots of choice among the Radeon HD 7850s. The Gigabyte card cools the best, but is very noisy. The XFX card is the most silent, but also very expensive. Sapphire has the best of all worlds in the Radeon HD 7850 OC 2GB. It's affordable, and has the second-best results both for cooling and noise production.
Sapphire also stands out among the HD Radeon 7870s. Both ASUS and MSI are too loud, so it's a battle between Sapphire and XFX in this category. If you're looking for extreme overclocking, then a better option is the MSI R7870 Hawk. This completely redesigned card has little added value on standard settings, but is very suited for the heavy work.
MSI R7870 Hawk
Sapphire Radeon HD 7850 OC 2GB
Sapphire Radeon HD 7870 GHz Edition OC 2GB