I did it the opposite way, as I already owned a Musical Fidelity CD PRE 24, which is a solid state preamp/CD player combo. I replaced a Musical Fidelity A300 power amp with a Prima Luna Prologue 5 tube amp.
With a tube power amp (36wpc), I notice that the sound is richer and fuller, but doesn't doesn't quite have the slam that a muscle power amp has (150 wpc).
One thing about doing it this way, I did not have to be concerned about output matching as Newbee mentioned above.
Regards, Rich