The Antec 900 already comes with 4 case fans, you don't need another.
The Phenom II chips are also dual channel so you still want 4 or 8 gigs(once again 4 is enough for a normal person.) Also the 955 is a better value. The 2 chips are identical really but the 965 stock speed is just set higher by AMD which is pointless if you plan on overclocking(you should.) This one is the latest stepping;
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103808
That motherboard is a bit outdated. There are newer AMD chipsets with 6 g/s SATA and USB3.0 which you will want. This would be a good choice;
http://www.newegg.com/Product/Product.aspx?Item=N82E16813131631
It also has a nice combo on a more appropriate PSU for your needs;
http://www.newegg.com/Product/ComboDealDetails.aspx?ItemList=Combo.437643
An 850w Corsair is only really needed if you plan on SLIing two GTX 470s and AMD motherboards don't support SLI so to do so you would need to switch back to an i5 system. OCZ is a good brand and 700w should let you easily crossfire 2 overclocked HD5850s.
That said I would recommend just getting one for now. A single OCed HD5850 should be very good for your resolution. So just get one and try it out. You can always order another if/when you find it necessary. Specifically I would recommend the Asus DirectCU version of the card. Here is a review;
http://www.legitreviews.com/article/1273/1/
It is currently out of stock on newegg but it is available at amazon;
http://www.amazon.com/ASUS-EAH5850-DirectCU-2DIS-1GD5/dp/B003AVBSXE
Lastly if you have the money(and you seem to especially if you follow my suggestions) you may want to consider a small solid state hard drive for your OS and most commonly used applications/games. It will speed up the system in general and especially load times for Windows/apps/games.