Once you start to pre boost to 320v or so, you have lost all the advantages of the LF inverter topology. I would never build a hf inverter, as it is just an inverter... and a poorly regulated one at that.
When you have to rely on the energy storage of your HV caps and the throughput of your step up stage, we find very limited surge.... and straight away we have made running many highly inductive devices problematic... like single phase induction motors of any size etc.
The big advantage of lf inverters is that you have the entire battery as the surge energy storage, so you can be running a pretty heavy house load regime, and still start a compressor or boil a 3kw jug, while the water pump turns on and run the welder etc etc etc.
You also forgo the advantage of using reverse grid tie, which is very handy too, and allows for huge house loads during the day, without even loading the inverter up.... your 3kw aero sharps are perfect for this..... like running air conditioning all day while the aero sharp actually runs it and charges the batteries all at once.... so no....not step up for me.
I have made a small 3ph BLDC motor drive from a mc33033, and it had a pwm power supply to simplify the high side drive, and provide a isolated supply to both the three high side drivers, and the low side too. It totally isolates the drivers from spurious stuff in the power supply, which is god when you start using lots of power... so I gravitate to this sort of thing, and thats also why I like the PJ controller. It can be making a mess of the battery line, while the control is effectively totally isolated form the hash at 15kw and beyond in the surges.
So I will probably go that route, and leave the current pump style to the others.
I have the eg810 to play with, but may never get there... I have so many inverters now from experimenting, and they are all 6kw plus.... makes it hard to justify really, but curiosity is still there.
here is my bldc driver board with the 3842 pwm power supply. 5 outputs, three for the high sides, and two for house keeping and low side.
............oztules