Er... are the FZ-20 or FZ-30 dSLRs?? Thought they were "prosumer" cameras just like your current one.
The FZ-20, "prosumer" as you put it, is my current one and in quite some areas outperforms a DSLR, as does yours. I was just backing you up.
An E500 is a dSLR. It has all the bells and whistles of the canon, plus the ultrasonic dust thing, and its cheaper, comes with more fittings.
There is also personal preference and quality to deal with. Dust is a right pain if it gets on the sensor a DSLR though. So far the only reccommendation is to change the lens holding it lens down, this does seem to work.
My point I was making with the zoom comparison is that Brummie owns a S5600... hes used to 10x zoom (300 and something mm), when he has a dSLR the first thing hell end up buying for a canon is another zoom lens so it gives him more reach.
The only real advantages are as I said, low light and combined with action. I had the same choice when I got the FZ-20 and decided to save the money. So far I havent been disappointed as in order to match it I would have to have spent several grand on lenses. There is a review of the FZ-30 being put up against a Canon eos-20D with this sort of lens assortment and there really wasnt much advantage for the Canon dispite the extra cost.
http://www.firingsquad.com/hardware/panasonic_lumix_dmc-fz30_canon_eos-20d_camera_shootout/
The Oly comes with one, it also comes with a lower zoom lens, and they both compliment each other, so he wont be stuck with dead ground in between the two lenses where hed need to buy another lens.
Peronally I wouldnt consider the 38-55 canon zoom, I would go for a 28-105 to go with the 90-200. This would provide an overlap with the shorter lens providing portrait use. An alternative make 80-300 zoom coupled with a 2x teleconverter should give acceptable performance up to 600mm