Which makes the biggest difference?

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.

Esoteric 03xd CD player WOW!!

@yyzsantabarbara 

Thanks for the links. 

It depends. The components that really matter are the: Streamer, DAC, Preamp and Amp. All matter. The biggest difference I have experience over the last ten years has been the streamer. I had been thinking it couldn’t matter. I was so wrong (just like every time I think something can’t matter). The reason the difference was so profound is I had very high quality, compatible CD player, DAC, preamp, and amp, and an inexpensive streamer. So introducing a compatible / synergistic streamer was profound… like a turntable it is all the way at the beginning of the signal path. If it is noisy and not high resolving, the problem doesn’t get fixed along the way. So, this is really important.

On the other hand, the preamp is the heart of the system, it’s boost from line level sets the character. At the center of every great system is a really fantastic preamp.

But a really good DAC is required as it crafted the digits into the sound you are going to hear.

You don’t want the rest of the signal chain down.