If you hooked up your amplifier directly from the output of a CD player or DAC you would blow out your speakers. A CD player puts out a signal of 2 volts max and a power amp reaches full power at about 1.4 to 2.0 volts. That said, a preamplifier with (any) gain would make things much worse. That is why preamplifiers cut the voltage from the source through the volume pot and then gain up that divided voltage out to the amplifier.
An amplifier can reach full power from a CD source with just a linear volume pot before the amplifier. The only way a preamp can impede that is if it divides the voltage too low through a poorly designed volume control and that has nothing to with preamp gain or amplifier power.
An amplifier can reach full power from a CD source with just a linear volume pot before the amplifier. The only way a preamp can impede that is if it divides the voltage too low through a poorly designed volume control and that has nothing to with preamp gain or amplifier power.