I believe there is a perceptible difference in sq when using a reclocker like the Iris but that difference is small and subtle ... and the rest of the gear down the line would need to be able to display the differences as well
I think most people would be happy with ZS into the Ares via spdif
It’s a good sounding coax output on its own.
There are two other side benefits of using the Iris beyond any perceived quality differences :
1) I can run two systems off my Zen stream
Was harder to do that before … it required going into the ifi app and turning on or off the correct output
2) the buffering of the fpga in the Iris has eliminated all wifi signal glitches
they weren’t happening often but every now and then there would be an audible click or a dropout before. That hasn't happened since adding the Iris (it could also be the result of the high quality usb cable though, so unclear about the root cause of that benefit)