Generally there are two factors related to the amount of weight you can lift. Well maybe just one...loader lift rating.
For example you are not going to lift 2,000 lbs with a loader rated at 1,000 lbs. Why? Because the pressure relief valve will kick open and the loader will stall.
Additionally, the more you want to lift, the more weight you want behind the front axle as a counter ballance. So a manufacurer would not put a loader that could lift 10,000 lbs on a small tractor. It would be unsafe. The small tractor could do the work...maybe slowly due to GPM flow of the hydraulics, but it could. No, it really could not...all that would happen would be that the rear wheels would lift off the ground...since the tractor would weigh much less than the load...
I think the rule of thumb would read something like "Heavy lifts = heavy tractor." And heavy tractor usually means more HP.
So if you want to lift really heavy things, then you will end up with a really heavy lifter. Could be a tractor, a skid stear or something else...
Hope I did not repeat too much or what everyone else said... /forums/images/graemlins/blush.gif