Ive been looking at this myself as finances will keep us at the lower end of the market...
Cool Energy do have an inverter unit, but it's big (a boiler replacement unit really). I asked them if they had plans for a smaller inverter but they refused to acknowledge the need stating that there was no real efficiency saving... Hmm.
Earth Save Products have a nice 11kW inverter, and Peak Energy are now branding the Lailey & Coates product, which has a nice simple-looking user interface
If you're looking for a 6kW unit, I made the group aware recently of a L&C unit that's currently available at a very good price.