Buy a navigation headunit or regular double din?

I am going to be buying a new car soon (2011 WRX) and to add a navigation headunit from the factory costs an extra $1,737. I am fairly certain I can find an aftermarket headunit that beats the snot out of any factory headunit for far less than $1,737.

I would like something that has a great interface , looks nice, and if possible can work with built in steering wheel bluetooth/audio controls ?