You may want to consider NordicTrack Tread Climber. It combines a treadmill, stair climber and elliptical. I don't own one myself, but I am saving for one!!
The advertisements look fantastic and although some people have complained about having problems setting it up, I think that is a minor annoyance.
Good Luck with your decision!
edited to add...I don't work for NordicTrack or anything...I just like this product