Musical Fidelity are more refined then the B&K (amps that is),each Musical Fidelity amp I have heard was nothing less than great,smooth and not overly so and very detailed. Your call if you seriously hear an audible gain and have no regrets ..go for it. It there is doubt,stay with the B&K.
Where I am sure you would be making a serious jump is with a Celeste MOON Titan power amp. But here the size and price puts it in the ubber class.
Klipsch,Dynaudio,Paradigm Signature,Pioneer Elite,Krell,Tenor Audio,Anthem Statement,SimAudio MOON,Parasound HALO,Bryston,ATI,Onkyo Integra,Denon,JL Audio,Sunfire,TC Sounds,Acoupower,QSC PowerLight,Crown iTech,Furman,Chang,PS Audio and more in the house.
Too much gear,never too much music.