I can't answer the original question definitively, but in terms of upgrading I'd suggest either:-
a) Chording the NDX (e.g. Hugo, Hugo 2, or higher - though at the moment there seems to be expectation in some quarters that H2 might mean less benefit of the money going higher)
b) Upgrading the speakers: if you love the sound of the PMCs then better ones of that brand would very likely bring benefits as they have been continuously debpveloping their speakers over the years - for maximum benefit I woukd suggest considering secondhand or ex-dem.
Ideally of course, you would want to hear the benefit of a) vs b) with whatever under b) seems suitable.
