For a replacement air conditioner, a 15,000 Btu capacity is as good as it gets. If you really want additional cooling beyond that you would be looking at adding an additional unit.
For a replacement for your Dometic, or for adding a new unit, I recommend the Furrion Chill HE Replacement RV Air Conditioner # FR42PV. This is compatible with your current Dometic setup so replacement will be fairly simple. It includes a start capacitor to help jump-start the AC and the rubber dampeners really... view full answer...