As for bodies, timing is a little off for buying D200 new. For D300, you've be on a waiting list for months before you can get on. The D300/24mm would be a killer combo. You can add either lens above to make a good starting kit. D200 is already a good camera. If you run across a good used one, it would be a great buy. Those run for about $1000-$1100.
I've used both Canon and Nikon. Both, in the right hands, can deliver good photos. Personally I like the ergonomics of Nikon much better. A couple quick facts: with Canon, the power switch is on the lower back (with the 20d/30d/40d series). I constantly forgot to turn it off. With nikon, the power switch is right at the finger tip. Same with the control dials. Nikon camera comes with LCD protector. D200/D300 is weather proof. 30D is not. Nikon flash system still has an advantage over Canon. Canon has a tendency to abandon loyal users by changing designs. The EF-s lens mount is an exmaple. Canon has shorter product life cycle. It's a like it or hate it thing. The Canon wins with the quick control wheel.
Anyway, hope this helps.