Oops, I had to move the Modius from my desktop system. I still believe it is a great DAC for the price, this was simply a case of poor synergy. My headphone system benefits from a warmer sounding DAC. I have moved it to a secondary speaker system upstairs (RPi 3B+, Modius, Magni 3 preamp, Meitner STR-50 Plus, Raw-1F single-driver speakers). The Modius replaced a Modi 3 in this system, the Modi went to my "whole house" system connected via Toslink to a Chromecast Audio streamer. So both my speaker system and Chromecast systems benefitted from this change.
I am currently using the iOne in my main headphone system, where it is performing as it never has before. Previously, I had driven the iOne from a Raspberry Pi or a laptop, with auxiliary power from a wall wart. Powering it from a linear power supply via the sMS-200's very clean USB port, along with a couple of cable tweaks made all the difference. I believe the iOne benefitted more from the clean power than the Modius because of the way the Modius is designed. In the Modius FAQ, they say this:
Well, I’m gonna get me a fancy-shmantzy linear power supply, what do you think about that?
We think you’re a little strange, because the output of that fancy power supply is going into a switcher, anyway. But if it makes you happy, we’re not going to stop you. Nor will we try to sell you such a power supply.
The Modius sound did not change, whether I used the supplied wall wart or USB power from the sms. The iOne changed a great deal. My Raspberry Pi 3B+ and Dell Inspiron laptop both have awful USB power. Because the Modius (and Modi) use power from the wall wart when it is connected, the dirty power from the upstream computer is bypassed. This is an advantage in some systems, but negates the value of a super clean source like the sMS/LPS combo.