Very good point about sensitivity matching. Noise or hum that is barely audible on 90dB speakers may be objectionable with 96dB speakers. My Dennis Had amp both needs a preamp and is not 100% silent. Consequently it works better with medium-high efficiency speakers (20 wpc and 90dB is a good combo in my room). On the other hand, my Oliver Sayes/FI 421A SET has an input sensitivity of 0.65V and is D-E-A-D quiet. I only use a unity gain tube preamp for the remote control. My DAC puts out about 2.5V, so there is not only no need for gain there is no room for it.