No.1 you want the cool water coming from the RAD to go straight to your CPU.
In regards to the 1200. Yes it's big, but because of that obnoxious fan on top you essentially lose the entire top panel as a place to mount a rad. Same goes with the bottom mounted psu, you lost the bottom of the case.
This then leaves you with the front and the back, neither of which will easily allow you to mount a large radiator internally without some serious modding.
The Haf and the Cosmos S are both great choices.