Which makes the biggest difference?

the fuses... always the fuses

No one mention the source server, i think impact of the server on the chain is very listenable.also my experience with or without pre-amplifier goes toward with(good) pre-amplifier.

Power cable.

The DAC would make the biggest difference. It is your "primary source."

Sending an inferior signal to a high-perfomance amplifier will only reveal the deficiencies of the DAC.

rvpiano, when it comes to electronic components the amplifier choice is very important because differences in performance on any given set of loudspeakers can result in marked frequency response shifts and issues with power delivery. Given well made and designed equipment, of which there is a ton, other differences are relatively minor until you get to the world of turntables. The best insurance is to get an amp which can drive anything.