Never buy XFX GPU's. Their customer service is god awful. Their PSU's are great though. B-Grade is only 90 days. You take the risk on b-grade. That's why it's so cheap.
Do you think buying the ocuk 680 would be safest option as the warranty would be with them?
Ps last week my friend just got refused warranty on his xfx psu the shop wouldn't take it back because it was just after a year and xfx said it could only go back to the shop.