If I might contribute my 1.5cents worth:

1. The D200 is clearly the better camera especially because of
   (i) the bigger+better sensor
   (ii) the weatherisation
   (iii)  the much improved auto-focus.

What is more, as mentioned above, the D200 will surely become substatially cheaper in the next few months as:
(i) other companies bring out models with the same 10MP sensor - Pentax and surely Sony?
(ii) Nikon brings out a replacement for the D70/D70s that surely will also use the same Sony-made 10MP sensor that shoulod become the industry standard, as the 6MP sensor in the D70 was until now (except for Can*n of course). My guess is that a D70s replacement will be anounced at Photokina (late summer).

Therefor, you must ask yourself to what extent you really NEED a better camera than your D70? IMHO, the 6MPs are perfectly adequate for amateur use, for RR & for prints up to A4 at least.
I would therefore go for the new glass (according to your needs/desires but I would only buy the really good+expensive models so that you will be able to go on using them with your better camera when you do trade up.

Sorry for going on at such length (professional disease I'm afraid)

Yours,

Charles

Charles