Thanks for the link, you're correct they want to pull 2KVa out of a box no bigger than 40 cubic inches. These guys (http://www.apparent.com/products/) have what I consider a very workable technology, basically 2W/cubic inch but one inverter per panel. Since you have to have panels anyway, having the panel produce power directly in the form you want eliminates the need for size as the panel is compelled to be a certain size anyway.
But instead of changing the question (and age old trick of engineers to arrive at a feasible solution :-) The push here seems to be about efficiency. 95% efficient would be a huge improvement.
Whatever they go with, the tech is going to make a really killer subwoofer amp.
Looking at the requirements (mostly the high DC input) it seems that an IGBT class-D would be the logical starting point, but those are hampered by a 150kHz-ish max switching rate. I think Don Lancaster's Magic Sinewaves (http://www.tinaja.com/magsn01.shtml) meet the distortion requirements while offering the slowest switching requirements.
But instead of changing the question (and age old trick of engineers to arrive at a feasible solution :-) The push here seems to be about efficiency. 95% efficient would be a huge improvement.