First thing the PSU's going to do is rectify and smooth the incoming supply anyway. It'd be interesting (maybe?) to see what the incoming rectified-to-DC rail looks like when fed by AC, "pure sine", "modified sine" and DC (which you may be able to tap out of your inverter's own HVDC rail).
Watch out if tapping the inverter's DC rail though, they can take a while to discharge. I fitted a neon warning/power indicator to mine which brings it down to safer levels fairly quickly.
I don't know what effect, if any, modified sine or DC would have on any input chokes ahead of the rectifier. I've seen a CFL driver with a single-winding inductor in series with the mains supply. Double-winding (both supply sides) would cancel out, but single winding = electromagnet?
(guess who needs to learn about inductors properly :p)