Preamps... understanding volume...

Amps are limited, in absolute terms, by

• The voltage rails in the power supplies. These provide the maximum + and - V swing.
  
• The current available from their own power supplies, before those rails sag
  
• Thermally limited in the amount of power they can output before they shut off or melt.This is why peak power may be much  greater than continuous, as well as limit the ability to deliver into low impedance loads.
  

Amps are also a fixed voltage gain. Often around 28 dB. So:
Output = ( Input + 28 dB ) OR ( MAX)
whichever is less.

erik,

does that mean a stronger input signal, from a preamp with more gain (less attenuation), boosted by amps +28db will result in higher volume output, especially important for lower sensitivity speakers like OP is asking about?

Elliott, to answer your question just above:

The gain of the preamp cannot change the amp’s maximum power capability, of course. If the maximum output voltage of the source when boosted by the gain of the preamp is enough voltage to drive the amp to its maximum power capability, additional gain will just result in the amp providing that amount of power, or a given lesser amount of power, at a lower setting of the volume control than would be the case if the preamp’s gain were lower.

The maximum output power capability of the amp, into an 8 ohm or 4 ohm resistive load, corresponds to its rated continuous power capability into those impedances, plus whatever margin may be built into those ratings, plus whatever amount of dynamic headroom the amp can provide for limited amounts of time, plus or minus whatever presumably small differences may exist between different examples of the same make and model.

Regards,
-- Al