I have a feeling that the Stagea rear end and Skyline rear end are the same - ie. multi links, and as such will be toilet for towing a boat.
So as much as i like them, they are really no better than your skyline in terms of the needs you want - basically a skyline with a boot.
As for the Gen III, I know that a great deal of them have oil consumption problems, due to shit rings and poor running in. They tend to develop piston slap, and this is not limited to the old ones, the current gen 3 still have the problem (though much less common, a problem all the same).
The benefit of buying a late model is that you will be able to diagnose any case of slap straight away, and determine if it is using oil.
As much as I don't like gen III's, a good example is a strong motor - I have seen supercharged examples at 6psi making 220+ rwkW on standard internals - all they need is engine management to keep them from detonating.
Hope that adds.