Placing rad in the bottom will kill airflow. Placing it in the front kills all the space for hard drives, and will also heat your internals.

Outside is most "xtreme" in the sense it gives the best performance. You may get several degrees by strategically placing rad over the roof. As they say, "this will give your case unique look". Another advantage, you may place 2 120.3 here for two loops or better cooling in one loop.