You are right Rich, the Focal's do indeed have a built in DAC, but the DAC1 sounds better.
I really wasn't expecting any huge gains in sound quality, I was more interested in not having to switch back and forth between the two sources, but I was pleasantly surprised.
As an added bonus, the noise floor is apparently lower using the DAC1.
My next experiment is to use the optical output from the iMac into the DAC1 to isolate the computer from the audio systems. As of now, the iMac, DAC1, and XS are all on different outlets. By using an optical cable, I can provide galvanic isolation between the computer and the audio systems.
BlueJeans make excellent cables too.