Ken 1649 and LAKings good advice.
One card to stay away from though it pains to say, is the Sapphire Dirt 3. There's been some cards that have gone out instead of Cayman chips like their supposed to be went out with Antilles chips. They were laser cut which disables the possibility of unlocking.
I'm not sure the exact reason for this. It could be shortage of Cayman and surplus of Antilles but a 6950 is supposed to be Cayman.
Anyway those who've received the Antilles versions with their Sapphire Dirt 3 GPU's have all been unsuccessful to unlock the shaders.
I would strongly suggest the Sapphire Toxic AMD 6950
over any other 6950 out there IMO. It's the safest bet and comes with the DUAL BIOS switch. One hell of a card.
Also last piece of suggestion, if you do go with a reference GPU, please keep in mind it may not be unlockable anyway. Odds are you will, but there have been some that couldn't.
If your honestly looking for 6970 performance and your not willing to take the slightest chance then please by all means buy a 6970. It's 100% going to give you the performance you want.
Vendors have been doing great sales on the 6950 due to the unlocking capabilities, but it's sort of a mixed bag. I'm speculating - the 6970 sales aren't as strong and their over stocked compared to the 6950's which are harder to find as they go quicker than a hot dog in a school of piranha.
I have a strong feeling they are starting to disable the shaders so their sales/revenue go higher and they can unload the 6970's before the next gen cards hit store shelves.
BTW, Zvejniex - Welcome to OCN