Radeon HD 7970 reference Power Color/ASUS/Sapphire

[Oversemper]

Hello, everybody!
Please, advise on vender to stick with in case of reference version of Radeon 7970.
Namely, it is the following models (the price of mine local store):
Power Color AX7970 3GBD5-2DH ~$432
ASUS HD7970-3GD5 ~$452
Sapphire 21197-00-40G ~$467
The price itself is secondary, what is primary – is a chance of successful overclocking in range of 1000-1100 MHz by core.
The system is ASUS P8Z77 Pro, i5 3570K@4.2GHz, PSU 550W 12V@35A, pretty good ventilated chassis (3 inlet, 2 outlet).
Around the upcoming spring I plan to go crossfire with somewhat 750W PSU.
Any advice on the matter will be much appreciated!

 

[COLGeek]

I would rank order the venders (in terms of quality) in this order: Sapphire, Asus, and then Power Color. I would recommend them in the same order as well.