I have 3 pending church projects where I will be using CBT 70J speakers with the extender box. These rooms are larger than your space and very live, so I need the additional LF pattern control, horsepower and bandwidth.
I demoed these, aong with the 100LA, a few months ago and was VERY impressed. For what they cost, they offer a lot of bang for the buck plus some versatility.
You can download the CBT array calculator from the JBL Pro website and probably get a good idea of how hight to hang them.