6850's in crossfire outpace 5850's in crossfire by a very significant margin in just about all titles at 1920x1200, despite the 5850 being faster as a single card. Chalk this up to crossfire improvements or other optimizations. [Edit: the Tom's review has a very limited set of benchmarks for crossfire results- check out the link towards the end for a more comprehensive comparison in differnt games and you'll see what I mean about the 6850 cf outpacing the 5850cf setup] The 6850's use less power, so they're WAY more energy efficient. Some considerations:
1) 6850's only require 1 6-pin PCI-e connector, where 5850's require 2 each. This may mean that you won't need to also upgrade your PSU if your current one only has 2 PCI'e connectors (likely if it's less than 750W).
2) What card are you using now?
Unless you already are running a single 5850 and would just be adding a 2nd, the 6850 is the better option. Better performance for right about the same money while using less power and requiring less PCI-e connectors! I'm running 2 5850's because I previously had 1 and found a good deal on a 2nd one. Not as fast as 6850's, but I was already halfway there.
The one drawback with dual 6850's is that it looks like they run quite warm and loud in crossfire. The Tom's review only shows noise/temp benchmarks for single cards (which I hope they change in future review!). Below is a link to the Guru3d article that shows these numbers.
This Review shows a 6850 starting at higher clocks and OCing to lower clocks than my 5850, which at it's stock lower clocks is faster than the 6850. So while CF 6850s scale a bit better (pretty slight according to most benchmarks) the performance increase on the 5850s is greater than on the 6850s.
I'd love to see someone post their OCed CF 6850 results tho, I really am curious how far they can be pushed (at least on air cooling)
Beltzy, you are perfectly right and I noticed it by myself while browsing them. Glad I did, I don't need a new power supply and that's a really nice feat. Also they use less power and they are dirt cheap here. I got 2 for 400$ with taxes and shipping and 350$ with the 15% of paypal for the boxing day at new egg.
As for the OC... I plan on having 2 and I am pretty much sure that you cannot OC a single 5850 significantly more than 2 6850 in CF at stock speed, sorry, but that's the logic here... unless you want to crap your PC.
I think you'll be very happy with your setup. Given the PSU situation I think what you decided on probably makes the most sense. Wolfram does makes a great point, and I'm certainly not going to argue with his benchies about his overclocked 5850's. However, sounds like a pretty significant OC and a lot of folks aren't as comfortable pushing their GPUs that far, changing voltages, etc.
Thanks to wolfram- I learned something from this thread as well! Would you mind following up with a bit more info about your OC'd cards? Did you use MSI Afterburner? What kind of voltage changes did you use (if any)? What clocks did you settle on? I may start playing with a bit more of an OC on my 5850's. Cheers.