You have a nice setup. I have the same Mac Mini with Uptone MMK. Mine is powered by a Paul Hynes SR7. OSX is run off SD card and music drive is streamed from a Thunderbolt drive.
I have compared microRendu powered by the Paul Hynes SR7 against a recently purchased SOtM sMS-200 which is also powered by the SR7. Compared against the LPS-1, I have found the SR7 to be superior. USB cable used is a Clarity Cables Natural USB which is one of few USB cables that has been actually measured to meet true USB 2.0 spec (90 ohms differential impedance). This cable outperformed and replaced my Curious USB which outperformed and replaced my TotalDac USB. I have recently compared it against the RedNet 3 via SPDIF:
With each connected to my Chord DAVE, RedNet 3 sounded very good, a bit better than the microRendu with iFi 9V PSU. As you suggested, details were a bit cleaner. With the microRendu powered by the SR7, soundstage of the microRendu was much bigger with more air and much better dynamics but clarity with RedNet was still a bit better. In comparison, microRendu sounded a bit muffled. Which one is better between these two, I think it's a toss up. It depends on which qualities you value more.
The winner of the group by a fair margin, however, was the SOtM sMS-200 powered by the SR7. This is now my new reference front end with my DAVE and surpasses the microRendu by a fair margin and for less money ($450). In fact, it is the least expensive device of this group. It matched every bit the clarity and the smoothness of the RedNet but the soundstage was bigger still and with extraordinary dynamics. Compared to RedNet, RedNet sounds flat. Treble edge or glare? I'm not hearing any of it. This device is very clean and the PSU has a lot to do with it. Part of this is almost certainly due to DAVE's exceptional USB implementation which incorporates galvanic isolation. While the RedNet 3 holds much promise, I suspect its downfall is its PSU.
Regarding your system, consider replacing your HDPlex. With your Mac Mini, you will be quite surprised how much better the Paul Hynes supplies are. I say this because I have an HDPlex also in addition to a Teradak, Paul Pang, Kenneth Lau and LPS-1. None of them are in the SR7's league. Since Paul Hynes is based in Scotland, it should be easier for you to audition one.