Your motherboard runs its second PCI-E 16x slot at 4x speed, so you can't use it for Crossfire. If you want Crossfire support, you'll have to upgrade to a board that runs at 8x speed for both slots. If you don't need/want Crossfire support, you don't need anywhere near 850W. A quality 550W - 600W PSU would be plenty.
Since gaming is your first priority, the i7 860 might be overkill. If I had your budget, I would get the the Phenom II X4 955 with an AM3 mobo. For the GPU i would get the HD 5850. Then I'd overclock the 955 to 3.7, 3.8 Ghz. At that speed, the framerates are near equal if not faster that what i7 860 would push out.
The money I would save would go towards to two additional 23" monitors. You already know what's coming - eyefinity! With that budget, why game on one monitor? Have you seen the eyefinity demos on Youtube?
you are all wierd who ever said i5 750 +1, 860 vs 750 vs 955 vs 920 are all about the same in gaming, so get the cheapest one, 955 or 750, but since the 750 beats the 955 pretty badly in sythetics, and costs like 20$ more, go with the i5 750. how did dual monitors eyefinity get involved in this??? the 5850 is an extremely capable card, but madadmiral is right, it wont be able to handle hd eyefinity crysis, and some others. on a single monitor it kills, so just stick to one monitor.
theres showing that a 750 is great on games, and go back a little to see how great it is on everything else. and yep, i would rather play on 1 monitor too, i hate having the bezels in the middle, and its like playing on a tv, i just like my nice 25.5 incher
I'll have to do more research sonce MadAdmiral brought up a good point that the 5850 might not be the best GPU for Eyefinity.
Eyefinity doesn't exactly lend itself to a budget.
I know that THG has their Best Graphics Cards for the Money list, and that typically suggests resolutions along with the cards. The 5850 gets honorable mention at its price point, and they say that it is exceptional at 1900x1200 and can do 2560x1600 for most titles. You might also take a look at the graphics card charts as well.