I did wonder after KeepIS mentioned the power levels he was getting ... that using a single 3kW toroid that was fully stripped and then rewound with the ideal number of turns and gauge of wire, may give an even more efficient outcome again. Unless of course what's already on the core is the ideal, which would have to be a massive coincidence.
I don't have enough experience with household loads yet, but what you described makes sense.
One other thing is that Aerosharp sold 1.5, 2 and 3kW units ... so if KeepIs was using a 2kW toroid and you use a 3kW ... that's a bigger step up than 2.5 to 3 ... unless of course his was a 3kW toroid already.
Just out of interest, the girl at the place where we used to get our scrap Aerosharps was adamant that they also made a 5kW version but she had never seen one. I just searched and they did actually make one, though no idea if there were many or even any in Australia.
Anyway, if you have a 3kW core and we can find the right wire, I'm happy to wind one for you.