All of the DACs were connected to my PC using the exact same model of 6' USB cable from Monoprice. They were all connected to the Niles AXP-1 5-way switch (and then the Benchmark DAC 2 dual analog inputs after I wore out the Niles switch), via the same 3-ft Monoprice RCA cables. All of the RCA cables and the Niles switch were tested for volume drop vs. running directly from one of the DACs to the Amp using my ~25-yr-old Monster interconnects. As long as I had a good connection, there was no volume drop as a result of running through the system, and I believe that those connections were delivering an accurate signal to the amp.
For those getting ready to complain about the cables, I don't believe that magic cables would reveal any differences in these DACs. Moreover, based on all of the arguments about cables over the years, whatever cables I would have chosen, somebody would have complained about them, because every cable out there seems to have both proponents and detractors. Different types of analog cables might sound slightly different from each other, but I don't think these relatively short cables were degrading the sound in any way, and as long as I was using the same cables for all of the DACS, this setup offered a fair basis for comparison.