No one has mentioned the 270's yet. Here's my experience:
Asus R9 270 : Unlocked. 1.100/1030/1400 = 440 kh 7 days stable. 120 W draw per card
Gigabyte R9 270: VOLTAGE LOCKED!
Tried 1.100v and 1.150v in VBE7, flashed BIOS, no errors, but the cards hang on boot when X starts. Running stock, these cards draw 30w more per card than the Asus 270's, for a just a slight 10 kh improvement.
On top of that the Asus cards are quieter and cooler.
Asus R9 270 : Unlocked. 1.100/1030/1400 = 440 kh 7 days stable. 120 W draw per card
Gigabyte R9 270: VOLTAGE LOCKED!
Tried 1.100v and 1.150v in VBE7, flashed BIOS, no errors, but the cards hang on boot when X starts. Running stock, these cards draw 30w more per card than the Asus 270's, for a just a slight 10 kh improvement.On top of that the Asus cards are quieter and cooler.