Don't forget...you can rent some of these lenses and see what works best before you buy.
I've seen a few of the 12-24mm Nikkor lenses for pretty nice prices well within your budget lately.
Until going FF, I make quite a few nice and large landscapes with this lens. It more than paid for itself shortly after its purchase. It worked well on my D300/s and D2x. I still have it awaiting the D300 replacement.
Yes, I may need to rent and try some of these lenses out.
I wonder if that D400 will ever come... My eyes keep drifting over to Fuji, Olympus, and Sony...