I have a Pontus II as well, and I also love it; additionally, I have a PL preamp and PL power amps, so I think my experience will be relevant to your questions. I have an Iris DDC, but after doing the experiment described below, I no longer use it. I am streaming Qobuz via Roon, so all I really need is a simple Roon endpoint. I had been using an RPI4 running RopieeeXL, and sending the USB output of that to the Iris, and the I2S from the Iris to the Pontus II.
However, I had been curious about the new Mercury V2 streamer, which has direct I2S output. I wanted to see if going direct from the Mercury via I2S would sound better than having to do reclocking and a protocol conversion in the Iris DDC.
I compared these two means of getting a digital stream to the preamp:
- The Mercury, running RopieeeXL, with I2S directly to the Pontus II using an AudioQuest HDMI cable.
- An RPI4 running RopieeeXL, with USB output (WireWorld USB cable) into the Denafrips Iris DDC, whose I2S output then feeds the Denafrips Pontus II (AudioQuest HDMI cable).
Both the Mercury and the RPI4 connected to the same Roon server; both were running RopieeeXL, and the LVDS switches on the Mercury were set so that the Denafrips did not require re-configuration when systems were swapped.
The rest of my system consists of a PL EVO 300 preamp, and then two PL EVO 100 stereo power amps, each one driving a DALI Epicon 6 in vertical bi-amped mode. I also use a pair of Rythmik F12G subs. Roon is served from an i7 Mac Mini that I installed Linux on, and then installed Roon Server.
I switched back and forth between the two setups repeatedly, using a variety of my favorite test tracks. I found the Mercury has similar low end sonics to the RPI4 -- perhaps a slightly more defined attack on, for example, drums -- but there was a noticeable difference in the high end, particularly the attack on light percussion such as sticks, as well as better low level detail in things such as woodwind instruments and faint cymbal swells. This extra detail did not come with any harshness. The enhanced higher frequency sonics lead me to believe that the direct to I2S configuration of the Mercury is substantially more accurate than the reclocking from USB to I2S in the DDC; the precision timing information most likely leads to the increased resolution.
I have retired the Iris and now stream directly from the Mercury V2 to the Pontus II using the I2S connections. I would highly recommend that configuration. Philosophically, having as little equipment as possible between the raw bits and the DAC seems to yield a simplicity that translates to good sound.