Newbie Question About Nikon Lens Line

Greetings. I am a "serious amateur" who presently uses a Konica-Minolta A-2. I always intended that camera to be a short-term bridge from film to a DSLR and now I think I have arrived at that point.

I've been lurking here for several weeks and it seems obvious that I'll be really, really sorry if I throw almost $2K US at a D300 but then put a cheap lens on the camera. Therefore I am hoping some Nikon veterans can help me decipher the differences between the various Nikon lens categories.

The A-2 has a built-in 28-200 (SLR equivalent) lens and in the 3 years I've had it I have seldom wished for anything wider or longer. Unfortunately I get the feeling from browsing this forum that any 28-200 "all-in-one" zoom is going to be a risky compromise with suspect image quality. Therefore I'm thinking I will need to buy two zooms: a 24-70 or 28-80, and a 70-200, 80-200, or 70-300.

Which Nikon lens model line should I be looking at? If I buy the D300, do I want DX lenses? Why or why not?