Is a NAP150X an upgrade for a Unitilite?

My guess is that it would be an improvement, if only because the power amp then has some distance from the rest of the electronics, in addition to (probably) being inherently better than the UL built in one. Naim suggest the current 155XS as an upgrade, so there is a pretty good chance its predecessor would be too, as long as it's not old enough to need a service.

Thanks - that's a good point re the 155. 

Has anyone done this / experienced the difference?