Value and ConclusionAt this time AMD's Radeon HD 6850 seems to be the most affordable high-performance multi-card setup out there. It offers the possibility of getting one HD 6850 card today: win because it's price/performance king and has enough steam to let you play all the latest games at resolutions up to, including, 1680x1050 well into next year. Should you then require a more capable gaming rig, you can just grab another HD 6850 that should be even cheaper by then and keep on gaming. But at this point your setup will be maxxed out, you can not just add a third or fourth card like the HD 5800 series allowed you to do.
Another important point here is that AMD has more cards coming which will probably put the performance of this CrossFire setup into a single card, and you will be able to CrossFire two, three or four of them. So the bottom line is that right now you shouldn't invest into a HD 6850 CrossFire setup, but don't be afraid to buy the single card now if its expandability options don't seem to be an issue for you. There will always be something new at the horizon, rather start gaming now than play the waiting game.