Since posting the original question I have had the opportunity to directly compare the Bartok to the Rossini and this is what i found:
Bartok (classic mapper) ==> Rossini (MAP 2)…… big improvement - better etched, lower noise floor, more low level detail, transients apparently quicker, instrument decay better defined and most important cleaner better defined bass making all music flow more convincingly.
Bartok (classic mapper) + Rossini clock ==> Rossini (MAP 2) without clock ==> Rossini still much better - makes much more convincing music exhibiting much better drive or ‘PRAT’ and with more detail than the Bartok. The Rossini is very good without the help of the clock.
Rossini (MAP 2) ==> Rossini (MAP 2) + Rossini Clock ==> big improvements to soundstage depth and space around instruments.
Rossini (MAP 2). ==>. Rossini MAP 1 / 3 ===> much increased resolution and much wider soundstage. I prefer MAP 3. MAP 1 and 3 allow much greater insight into the way the instruments are being played - for example you can easily hear differences in the way a piano key is being pressed or a guitar string plucked that was less distinct through MAP2 and very faint / missing through the Bartok. Piano works now sound sublime through the Rossini.
Rossini (MAP 3) + Rossini clock ==> Seriously good sound.
The Bartok is very good while the Rossini takes you a very long way further along the same trajectory (nature) and will increase your enjoyment of music significantly. I was very impressed and have now invested in my own unit.