I am building my new system very soon, The system will consist of these items (v) means i already own it.
Inel core i7 3770K
MSI Z77 Mpower BigBang. (v, ordered)
850W PSU (V)
ATI/AMD Radeon 6850 Crossfire (v, only one though)
16gb Vengeance RAM (v)
256GB SSD (V)
1TB HDD x2 (V)
My question is, would this system be ok, providing that i have an ASUS 6850 (which i already own) and another makes 6850, e.g. XFX.
I am not buying another ASUS 6850, i got mine when they were £89, now they are £160! I am not willing to pay that much the same card, when i can purchase a card with nearly 30% better performance for a similar price.
XFX are doing these for £94, which i am quite happy to pay for a card of the standard.
You can crossfire any hd6850 with any hd6850 so you should have no problems at all getting a card from a different brand. In fact you can crossfire cards that are in the same family, like a hd6850 with a hd6870. If one of the cards is running at a higher speed then the other, then the faster card will simply downclock to the speed of the slower card. However you can tweak the clocks a bit (if they are to be a bit different) and you will get your optimal performance. Your psu (assuming its of a good brand) is more than enough to run two hd6850's. So you are good to go.