Super Telephoto lens

If I were to buy a super telephoto lens I think I would get a 500mm. It would work well with a camera with full frame sensor features, which is the route I would like to go. It also is a bit lighter and most important to me, a but cheaper than the 600mm. Unfortunately I don't have an extra few thousand dollars laying around, and if I did I think I'd end up blowing it on a snowmobile. By going this route I will be able to access much more interesting secluded scenes for landscape shots. Most wildlife in the area probably won't stick around, but I won't have the proper lens to tightly frame them any way.