I have posted a few times the last week trying to get some advice on a build for a gaming rig. I will be playing Warhammer Online mostly, but enjoy lots of other games as well. So far this is the build i have put together with the help of people on this forum so far. If there is anything that wont work, or something I can upgrade for about the same price, let me know. I am not experienced with over clocking either, just FYI. And would a Full tower work better? I left the names of the items off the page, because honestly I'm not sure what part of the information to post, so I did links.
The antec 900 should work fine with your build, the only reason to go full tower is if you want to have alot of extra room to easily fit your stuff in. Whereas with a mid tower it might get slightly cramped, which isn't much of a problem especially if you do some cable routing.
Also your motherboard is great for running 2 graphics cards if you do choose to do that later on.