I personally would go with a front Aussie. If you're still pretty stock it will be a win/win upgrade since you have the CAD Dana 30. When in 2WD you won't even notice it on the street, but will be more helpful than just about anything else on the trails. I personally think a front locker is more ideal because I like the wheels that are directing the Jeep to be the ones with the most control.
Selectables are great and offer more control, but are expensive/more complicated. If you have plans for down the road to swap in TJ shafts then a selectable would be ideal, but since I decided to keep the CAD I went with a Lock Right in the front and absolutely love it.