Lens advise from all who shoot landscape...

[Joves]

Sell one of those bodies (probably D80) and pick up a film body (I got my F100 used for $280), some Velvia 50 film (very vivid colors), and a 24mm f/2.8. Slight distortion is good I think to lend attention to the subject.

You should not be shooting landscapes with digital. You can, of course, but it's not ideal.

Yes but you can download a set of programs that will be the same as Velvia. Actually coming from film I find digital to be much more ideal myself. My film camera is now a piece of shelf art.
To the OP well you can shoot waterfalls with any of the lenses you have listed. What you might add to them is a good variable ND filter. The Singh-Ray comes to mind, expensive for a filter yes but, the best. If you want wide field then there is always the 10.5 fisheye. You can flatten the field later. There are several programs out there to do that. You cant get much wider than 180 degrees.