Which SLR

I'm vaguely thinking about upgrading my SLR, currently a Nikon D50, and possibly going over to Canon, because there seems to be more reasonably priced Canon gear around and because it's easier to test older lenses on Canon than on Nikon - the adopters are simpler and cheaper because the camera body is shallower. Another factor is that the lens I use most is designed for the older Nikon autofocus bodies with a motor in the body and is incompatible with most recent bodies, so I'd need to change it if I got a newer camera - if I do this I might as well go the whole hog.

My needs, basically, are a body with reasonable resolution - say 10 megapixel or better - and a macro zoom covering say 28-200 or 300mm (my current one is 28-300) plus a smaller zoom (say 15-55mm) for family stuff where I don't want to lug around s big lens. Digital preview would be nice but I don't want to pay huge amounts for it. I'd be looking to buy 2nd hand so reliability would be a plus.

Recommendations?