Path to an ND555 set-up

I purchased my N272/250DR combo a couple of years ago with an upgrade journey set fair for an XPS DR or 555PS DR, a Fraim and some new speakers - a well-trodden path in these parts. Straightforward, or so I thought. Until Bert's thread.

I am probably not alone in being drawn to Bert's odyssey with his new ND555 (and the emergent experience of others). I too thank him for relaying every step, even though it now means I have my nose pressed firmly to a crowded window. That said, allocating sufficient funds for a full 500 series home for an ND555, in one go, would probably affect other priorities too much for now...

That said, 

I have heard 500 series systems and a very fine sounding 252/SC/NDX through S400s so I know that there is greater weight, texture and detail to be had above my already excellent set-up and this struck me as a transparent source first set-up that I could achieve without carpet-bombing the finances. 

I thought I should start this as a new thread and not hijack Bert's. 

David