I'll weigh in with my opinion. Maybe it will give you insight into the matter.
I started shooting film. Loved it and the smell of the darkroom. I resisted digital for quite a while, but eventually caved in and bought a D70. I noticed that my 50 1.4 lens gave me a different perspective on the crop camera...and I didn't like it. Eventually, I moved to the D200 and to the D300. Both were good cameras, but neither were good in low light. When I moved to the D700, I noticed that I got the same perspective of focal length that I got from my film cameras - which I really loved - and excellent low-light performance.
As the newer FX cameras came out, I decided to stick with the D700. In fact, I bought a second one when the prices started to drop. It was everything I needed.
I've read here and elsewhere about the improved technology. Aside from slightly better low light performance from the D700, the biggest improvements in my photography have come from practice and improvements in my technique. Yes, the newer FX and DX bodies have better dynamic range. This can be seen in numerous tests found on various internet sites. I've found that although the testers went to great lengths to display these technological improvements, the actual photographs really did not. Of course, I'm not a pixel peeper, so none of this matters to me.
I owned the D300/17-55 combo. The D700/24-70 combo is better. My copy of the lens is sharper wide open, and the D700 is better in low light. I also get the same perspective looking through the D700 viewfinder that I get looking through the finders on my film cameras. Those reasons were enough for me.
I also realize that my setup is a little bit heavier - which makes it cumbersome for daily use. To address this issue, I bought a D5100 and a couple lighter DX lenses. That's the kit I use for casual snapshots.
You already have a D70 and 55-200VR. I'd sell the 18-70 and pick up an 18-55 and possibly a 35 1.8. All three lenses are small, light, relatively inexpensive, and use matching 52mm filters. I'd also sell the D300 and 17-55 and go with the D700/24-70. You've already found a nice deal on the lightly used body around which you can build a fine kit. Go for it.