Just to be clear, the field of view of ALL lenses (FX or DX) mounted on a DX body gives the x1.5 magnification. It is due to the DX body and will happen even with DX lenses. So please do not confuse FOV with the focal length of the lens. 55mm DX lens and 55mm FX lens will work the same way on a DX body, just that on a FX body the DX lens might vignette.
Considering TS already has the 18-55, it does not make much sense for him to buy the 28-300 or 24-120 as there will be a large overlap unless he doesn't like changing lenses. I personally feel 24mm/28mm is not wide enough for landscape photography on a DX, which is why i have the 18-105 for those occasions.
The f numbers of all these lenses are similar at equivalent focal lengths, so I don't see much of an advantage in spending more money than a 70-300mm VR. It gives the 300mm reach, is reasonably light, is quite a bit cheaper, and covers from 70mm a little past where the 18-55 left off. And AF is quite fast. I have had an 18-200 and this focuses just as fast if not faster. Don't know about the 28-300 or 24-120. Btw, the 70-300mm vr does have manual override AF. It is a very good lens for its price. And you can buy the fast prime lens with the money left over which will usually give you much better quality than any of these zooms.
Caution: Read this with a pinch of salt. This is MY opinion only and is due to the direction I have taken, at the end of the day you should decide for yourself. Suggest trying the lenses out at the NSC before deciding.