If you mean between the Roc and Master-6 then there are significant improvements with the Master-6.
Dynamics are stunning from the M6 being fed by the NFB-7, this ain't background music!! I always felt dynamics were already very good with the Roc (about on par with the Woo6se) but the M6 is a clear step up.
The dynamics are stunning on the balanced LCD's so I expect a big improvement again when I balance the T1's.
I don't hear any hiss on the M6 at level 60 out of 70 which is at alevel far higher than I could listen to even on the HE-6's. So I would say that the M6 has a totally black 'blackground' but then I felt the Roc did as well. The Woo has the faintest of hiss at very high volume, higher than I could listen to.
Soundstaging seems naturally wide and deep. Nothing seems over emphasized.
Bass,one of the Master-6's strong points, is deeper,even tighter and with greater drive and impact and the sound generally if fuller and more powerfull with the M6.
Detail retreival is just stunning and absorbing.
I am mainly listening to the LCD's at the moment though for 2 reasons :-
They are new and they sound absolutely stunning