Best 6950 to bios flash and shader unlock

Just wondering what the best 6950 for bios flashing is, I know the MSI Frozr cant be flashed are there any other 6950 that cant be flashed ( I herd someone say the XFX cant be flashed also). Also can any of the NON reference cards be flashed.
I am happy with my R6950 overclocked, But i can swap it for pretty much any 6950 at work and want to get the coolest one. Ie Asus

I'd say any of the reference 2GB cards.
And you can rule out those without a dual bios switch or 1GB's.

The article below has a chart showing a list of cards that have been unlocked and flashed by manufacturer.

http://www.techpowerup.com/articles/overclocking/vidcard/159

Stay away from the Sapphire cards. I have a Gigabyte 6950 2gb flashed and unlocked no problems.

All the reference cards w/ dual bios switch can be flashed. The non reference cards can also have the shaders unlocked but it's more difficult due to no back up bios. But reports have confirmed that it's possible.

Stick to the reference designs to have the easiet time. Both my xfx and gigabyte cards are reference designs and unlocked fine.

The 1gb cards can also have shaders unlocked, but again riskier due to no back up.