Sunny Boy SPS?

[inetdog]

Unless you have a small microwave I doubt you will be able to start it with the SPS

Correct. The SPS has approximately zero surge capability. And the available output will drop below 1500 watts as the panel power decreases with time or weather.
So the 1500W output is more reliable over the course of the day if you have the 6000W unit and panels to match than if you have the 3000W unit.