The problem with the M1 as a preamp is the relatively low output RCA voltage (1.2V) going into my relatively lower gain, lower powered amps (First watt Sit-5 monos), probably not enough drive into my not super high efficiency speakers.
Bricasti 1.2v, 6 dbm
Lumin X2 - 3V
Grimm +12 dbm
I had the Bric running it max output a pretty high gain preamp (Cary SLp-05) and in that system it was loud enough, but it was close.

