You'd get a better MPEG decoder in the 82 as well as DVD-A. When I got my Panasonic 47wx52 it came with the 62. I sold of both my new 62 and 56 and got the 82. Haven't been happier
I have heard that some people are finding RP-82s in Canada, but there aren't many around. You could probably find some on E-Bay, but you'll pay more than the original manufacturer's price.
What are you looking for in your upgrade? If you were happy the RP-56, I would suggest the the Panny CP72. Better PQ (flicker bug fixed), addition of DVD-A and a changer to boot. Best of all, you can still find them! There's a $30 rebate if you buy before the end of the month too.
AFAIK, that was true w/ players using the fli2200 chip, but need not be true for new ones that use the fli23xx chip. The old chip did not offer scaling capabilities, so player makers would have to add a dedicated scaler chip, which they did not. The new chip offers the capabilities built-in, so player makers only need to design their players to use the functionality.
New and upcoming players known to use the new chip are the Philips 963sa, Samsung HD1000 and upcoming HD931. So far, it seems that both the Philips and the very expensive Sammy HD1000 don't quite do what we won't for plain letterboxed DVDs. Maybe if enough people complain and/or request it, the makers might offer firmware updates to address this, but don't hold your breath on it.
OTOH, these players do use the scaling and format conversion capabilities of the new chip for other things. For example, the Philips can do PAL->NTSC conversion and provides a pillar box mode for non-16x9 DVDs--and oddly, a non-linear stretch mode too. The Sammy's can upconvert to 720p and 1080i via their DVI output(!).