Asus, Sapphire or MSI, by far.
I'm unfamiliar with AFOX and Digital Alliance, as they must be regional brands - so read reviews.
Powercolor, His, and XFX all do 'meh' stuff; cheaper, but nothing special.
The only brand I recommend avoiding is Gigabyte. Their cards are generally decent (actually, their cards are admittedly as good as any of the top three, or occasionally better), but their customer service, if something does go wrong, is bloody awful, making them a gamble.
If you want quiet, get ASUS. If you want higher overclocks, go with MSI. Depending on the model, some of Sapphires cards are designed with significantly better VRMs, making them by far the best overclockers when water cooling... but that's probably not a factor when buying a 7750. :P