The Benchmark DAC1 is immune to jitter, but that does not mean that it "renders all differences between transports and cables irrelevant."
1) The transport must read the information from the disc accurately. Laser focus, disc stability, disc flatness in the transport, error correction algorythms, and variations in the disc speed all effect the accuracy of the read.
2) The data must be transmitted out of the transport and into the DAC without interference. The quality of cable and quality of output connector influence this.
I do agree that the DAC1's immunity from jitter eliminates the major variable in digital sound. However, I am still upgrading my old transport to the CEC 3300 so that I can use the AES/EBU 110 Ohm output directly into the DAC1. I can also use the optical and coaxial outputs and switch between them to see if any has an advantage.
Maybe they will all sound the same, but I would be surprised.
-Charlie