Compuwar,
We can throw all sorts of long fast lenses out there, but he stated his budget and your suggestions far exceed that.
The OP stated in their follow up that they didn't want to spend $3000 on lenses yet- the 70-200 isn't $3000.
The 70-200 is of limited use and will not cover all of what he wants to shoot.
His first two subjects are moving dogs and wildlife. No single lens will do well at all subjects (the 18-200 compromises optical quality to try to be all things in one lens, it's outperformed .) Everyone I know who shoots agility dogs professionally (fast moving dogs, sometimes inside with horrible lighting, sometimes outside) uses either the 70-200 or the 300/2.8. The 300/2.8 is well outside the OP's price range.
I don't know how much wildlife or canine activity you've shot, but I've shot a bunch, and I'll flat-out say that a lens that starts out at f/5.6 is a non-starter if you're not shooting in the mid-day sun- and you need 2 stops past that to get the 18-200 to be its sharpest- that puts you at f/11, the edge of diffraction on high-res bodies, let alone what AF is going to do in spotty light at f/5.6 (try and AF on a black dog.) The 18-200 is a fantastic travel lens, and a good all-around lens, but it's not a good fast dog or wildlife lens by two stops.
Secondly, the OP is the one who listed the 70-200 as a option, not something I'd expect them to do if it were outside of their budget.
My personal prefence of a 24-70 and a 70-200 would exceed his budget. So, the 18-200 is an excellent suggestion. Plus despite the fact that it is a bit slow, it is an excellent lens, don't overlook it's usefullness just because it doesn't have a gold ring.
"A bit slow" doesn't cover it- it needs 4 *times* as much light as the 70-200. The 70-200 along with an 18-55 or 18-70 is a much better solution- even a 35-70 isn't all that bad a choice if the OP's main subjects are moving animals and wildlife. The utility of a lens outside mid-day goes down significantly as its light requirements go up. It's the lack of a large aperture that makes the 18-200 not the right choice for animals or wildlife, combined with the fact that it wants stopped down one to two stops from f/5.6 to be it its sweet spot. That's not good for movement, and it's not good for subject isolation. Also, the 70-200 will perform acceptably with a 1.4x TC, making it usable for most wildlife outside of small songbirds in the wild.
In terms of pure resolution, if you look at Nikon's on MTFs, you can see that the 18-200's resolution drops off well before getting to the edge of the DX-sized frame, while the 70-200's is much, much better (note the scale different for FX and DX lenses- on a DX body, the 70-200 is all in the sweet spot):
http://imaging.nikon.com/products/i.../af-s_dx_vr_zoom18-200mmf_35-56g_if/index.htm
http://imaging.nikon.com/products/imaging/lineup/lens/af/zoom/af-s_vr_zoom70-200mmf_28g_if/index.htm
Finally, the 18-200 is a DX format lens, so if the OP decides they really do need the better low-light performance of an FX body, they'd be less-well covered by the 18-200 than by the 70-200.
You can shoot landscapes and architecture off a tripod (though the 18-200 needs a fair bit of correction if you're serious about your architecture) and not worry too much, wildlife doesn't give you the same range of options.
I won't say I've never sold wildlife shots done at f/5.6 or even f/6.3, but there's a heck of a difference in what and when you can shoot that slow, and there's a heck of a lot of difference in the results. As for AF on black or white dogs, even with an f/2.8 lens that's often a challenge- take two stops away from the AF sensors and you're going to have more misses.
We're just going to have to agree to disagree, but I'd bet I've spent more time shooting wildlife than anyone recommending an f/5.6 lens as anything other than a base compromise, let alone calling it "good."
