I own the Nikon D70 and have used/compared it with my brothers Nikon D200; whilst the D200 build quality is a lot nicer and indeed almost Pro standard, it is though, almost twice the price.
However, when directly comparing the images side by side I was surprised to find it is virtually impossible to tell which camera produced either one! I dare say, that you would eventually see a difference if you printed them both large enough! ie. Extremely large - But, what I'm getting at, is that the difference between 6mp and 10mp in image quality is not as wide as one would assume. Both Cameras can give the same stunning results.
The Nikon 18-70mm "Kit" lens is very good and I have to say that 18-200 VR lens is also superb and suits the D200 very well.
Personally, I think the quality of the lens is more important than the body.