This review shows that card 6850 maxing out at 127W (just under 11A):http://www.guru3d.com/article/msi-radeon-6850-review/8
Contrary to what you've listed for specs on that Corsair PSU, I see it as having one 12V rail with 30A and 360W total available for the 12V rail:http://www.corsair.com/builder-series-cx400.html
The 6850 only requires just under 11A max on the 12V rail. If Corsair used to make this supply with two rails and that's what you have, that is cutting it extremely close with the power requirement of your disk and fans. How many Amps did the review show available on the 1st +12V rail?
What does the sticker say on your power supply? One +12V or two?
Your CPU requires just under 11A (125W) and the 6850 requires just under 11A (127W). That's 22W leaving only 8 available for what your disks, fans and DVD require. If it only has one at 30A as the Corsair site indicates, you're still cutting it close. It will probably work, but if you get to the point where all those disks are in motion and if you have a bunch of fans and you put the max load on your GPU, it may start to show signs of a power issue. As a result, though that CX400 would suffice 95% of the time, I'd recommend a CX500 or better just to cover everything at full capacity. You don't want to create you're own little brown-out within your system. It could damage your components.