Replace Factory Power Inverter in 3rd Gen

So I already have power outlets in the cab and in the bed, I made sure I had the "premium audio package" which included the "AC Power Supply", but to be honest, its completely worthless, 100w? seriously? It will not even run either of my laptops (I don't use tiny little ultrabooks). The inverter button just trips out immediately.

So my questions are, where is this thing located? And can I replace it with at least a 400w true sine wave inverter?

thanks