aanthony
I use a fox evolution plus and am very satisfied with it,big enough for bedchair plus other gear. I think the fox evolution classic is very similar, I think it's not as big and cannot get a overwrap for it. you can set it high for more headroom or low to keep out wind,rain etc.Looking at the fox catalog, the stalker bivvy is the same size as my evolution plus, I believe with the stalker bivvy you have to thread the poles though,as far as length goes, my evoulution plus is a little over 6 foot when dismantled and very light,about 7 lbs and it fits down the center of my fox mega quiver, so the classic, stalker bivvy would probably be about the same
cannot comment on the nash shelters as I never seen or used one, but from what I hear about them, you'll probably still need to wear a raincoat while sitting inside of them
Hope this helps