Which 6950 for crossfire?

Both cards mentioned are solid 6950's. I generally recommend the Sapphire and it is a little cheaper but to be honest you cant go wrong with either. Yes the cards will fit on your mobo, place one in the dark blue PCIe 2.0 slot and the other in the white. You have a 2 slot gap between the cards so although they are double width cards you will still have sufficient room for airflow. And yes you can still fit a sound card.

Also make sure your PSU is capable.

My psu is 850W.

So I will put 2 of these sapphires cards on my dark blue and white slots and this sound card I'm considering:
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

on the black slot?

Also, do you know if these cards are unlockable/flashable? I know they have a dual bios configuration. I just would like to know if I can unlock them and overclock them both when technology catches up to these cards.

OK PSU should be fine.

Sound card should go in one of the dark blue PCIx1 slots, as your cards a double width it should go in the top slot.

The cards are not flashable. As in no you cannot unlock the shaders to effectively make it a 6970. The MSI does not have Dual BIOS as far as I know, please correct me if im wrong. The Sapphire does and its a great feature for overclocking, especially for the inexperienced.

Both cards will overclock well. The MSI is already overclocked by 50MHz, both clock and memory. The Sapphire is at stock speeds.

everything Ninja said is true, expect for the unlocking thing....
Sapphire HD 6950 Dirt 3 Edition has a Bios Switch and can be unlocked easily to HD 6970....

Both cards are great, but i always tend to go Sapphire i've been using their products since the X1900 and generally Sapphire is the best partner for AMD

another thing to confirm you're good to go, what's your CPU and the model of your PSU ?

Yea, I doubt I'll find any cards that are unlockable anymore. At least I can OC them when necessary. So what exactly does the dual bios switch do? One preset is fore stock clocks and the other one is your preference clocks?

Can I oc both cards?

Oh of course. I'm not sure if I'm going to unlock the cards I was just curious. I am new to overclocking as well, don't want to push the card too far and I think crossfiring these bad boys will play any game smooth as butter for a while.
CPU- i5 2500k

PSU-
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

you're good to go then, if you wanna overclock the cards just download the Sapphire Trix utility and increase the GPU clock by (20-30) MHz then increase the memory clock by 100 MHz and test stability (run games, benchmark utility, put the GPU on load)
if you're running fine without crashes you can try to go further, increase the core clock by xx and the memory clock by xx and test stability, you can do that until you're unstable (BSOD, crashes, freezing) and no matter what happens, don't mess with the GPU voltages...
and don't forget to check temps when overclocking

Thanks! This kind of changes the topic, but the other option I have is to wait till the 7xxx gpu's come out and I can crossfire 2 of those. It's an option, but I'm not sure if they're going to be buggy at all when they come out, and if there is anything that will beat 2 6950's CF for the same price.

AMD 7K series will be buggy ? (huh)
AMD 7K series are equipped with the new XDR2 rambus memory which is twice faster than GDDR5, in addition to the 1GHz GPU frequency, 28 nm process = less power & less heat... a high end GPU HD 7950 is said to be performing better than HD 6990.

but the AMD 7K series will be almost pushed to Q1 2012
AMD 6K series scales better than nvidia's GTX 5k series, 2 HD 6950s CF beat a single GTX 580

By buggy I meant it will have a lot of flaws, the first batch of cards usually have problems no?

Ah I see, than I'll just stick with the 6950 then. I'll upgrade sometime in 2013 then. 2-3 years is the usual longevity of these cards?

2 6950's are fine, I was just curious if by early december they would have cards better than a 6950 for 6950's current price. Most likely the 6950 will go down these next couple months, if I buy them on black friday hopefully I can get them at a steal!

so if you wanna wait, just wait to see benchmarks of the new AMD 7K series

The BIOS switch has nothing to do with unlocking (The second position is simply a protected copy of the factory default settings, The first obviously you can play with). But if you can "unlock" in the sense we are talking (BIOS flash to 6970) then please post the method because I feel there will be allot of people interested in this!

Might want to do a bit of research into Micro stutter. Nvidia boards seem to deal with it better in SLi.

look at this
i don't understand you...., anyway here's the method for unlocking the Dirt 3 edition
http://forums.guru3d.com/showthread.php?t=350307

The unlocking you are talking about has nothing to do with the BIOS switch on the card (this was what I was saying). Secondly if you read the comments on the link above they are correct, there are in fact two versions of this (6950 cards in general for that matter) available, well at least there was. Ones that could be unlocked and ones that can't. If you can still find one that can be unlocked your lucky (and tell me where I can get a few), but any new card you buy now cannot be unlocked via the BIOS flash outlined in your link. AMD where pretty quick onto this as one would expect.

In terms of microstutter, read this: http://www.tomshardware.com/reviews/radeon-geforce-stut.... It confirms what I think we all new and that is that Nvidia has a slight edge in this aspect and the better the card (cards) the less microstuttering. Neither SLI or CF solve the issue and given the results in the link above I fail to understand how this may effect the OPs card choice.

yes the unlocking has nothing to do with the BIOS switch ? but what does the BIOS switch do ? read "what if something goes wrong " in this article and you'll find out
http://www.techpowerup.com/articles/overclocking/vidcar...

Now you have confused me. That is exactly what I had been saying all along. I understood the point of contention to be the ability to unlock 6950's, which I said was only possible on the 'older' cards.

I saw a bunch of reviews on Amazon lately for that card. many people say they can't unlock this card any more. no BIOS switch on the card.

However, the sapphire HD 6950 toxic still has the dual BIOS switch and all 1536 shaders as far as i know.