I'm not 100% into photography so I'm not familiar with the lens that you list other than the 70-300 vr. I just picked up a D80 with the 18-70 lens and the 70-300vr.

The reason for responding here is to do just what you are doing. Ask others that have those lens. Also go to the camera shop and they should let you try it out. When we were purchasing our D80 the sales rep let us try a number of lens and spent over 2.5 hours with us to make sure we had what we wanted.

Another site I found with a good forum is http://www.dpreview.com/ On the left side is fourms and they have a spot for the d50, 70 and 80. You will get some good answers there.