Best practices when conducting a DAC comparison

The best measure for me to demonstrate the quality of the low end is the Beatles "Come Together" test. The first break where Paul let's his Bass "A" string linger out ("Joker do what he please"). Even if generally listening you cannot tell the differences between dacs, amps, cables....this one little passage will give it all away. You'll know it when you hit a sweet spot because you can feel growl of the bass string. You can switch components and notice that something is missing. This isolated bass snippet is copied and pasted a couple of times in the Beatles LOVE soundtrack as well.

........ is using the same cabling across the different DACs the best way forward?

OR

........ is it better to compare optimized systems, with the components standing on their own within them?

Both ways is technically best from a comparison and arrival at conclusion(s) perspective.

@david_ten,
I am rooting for the Terminator because I have been following it since its conception, it has been tempting my wallet for some time now.

How can somebody say that there will only be tiny differences between dacs? Maybe this guy hasn’t heard a lot of dacs. There can be big differences between dacs. Also, I don’t agree that you have to use the same cable or input to compare different dacs. If you are only using usb, then sure you have no choice, but if you have an option of using i2s, toslink, or spdif, then I would use the cable that the dac prefers because you want the best sounding dac that you can afford. I would never go back to usb, and I would tend to use i2s if possible.
Also, ignore all the measurement specs that some reviewers post, IMO they are worthless. Who cares if 1 dac has .0001% distortion and the other has .0005%, you think you are going to hear that? That’s like asking the Porsche dealer to give you a readout of the compression of each cylinder before you buy a new Porsche. You have the best instruments to do your evaluation and that your ears.

What I haven’t seen is your requirements for the dac and this is where you can get huge differences. Do you want the dac to support MQA? DSD and which resolution? I have some MQA tracks that surpass vinyl by not a small margin.
I would make sure that your volume levels are set the same and then test each dac with your favorite music using various inputs unless you are stuck with only 1 interface.