equipment recommendation - What's a good Nikon lens (DX) for a serious hobbyist landscape photographer?

I shoot a bit of everything, though mostly landscape stuff. Mostly with a beanbag, or handheld.

I currently have the following lenses:

The 18-70 is fine, but the 70-300 is cheap and slow, and I often find myself wanting to wider than 70mm with it (changing lenses is a hassle, and lets dust in).

For both of them, I often think VR would help, particularly in dim lighting (e.g. shaded forests, night shots, etc)

I've got two camera bodies, a D300s and a D70.

I've been considering the Nikon 18-200mm f/3.5-5.6 G IF DX VR, which goes for ~£545..£580

However, another option might be to get a 18-105mm f/3.5-5.6 G ED VR (~£220) plus a 55-200mm f4-5.6 G AF-S DX VR IF-ED (~£240), allowing one on each camera body - are there any advantages to that, compared to just the 18-200mm?

Are there any other lens options that make sense?

I don't really have a fixed budget, but anything over £600 is probably pushing it.

(The less money I can spend without getting rubbish, the better.)