Truly we are in the same configuration!We are in exactly the same situation, I also use the digital output at the same time as the subout. In fact, the new beta that allows you to use the USB at the same time with the Wiim subout is really a bomb. It allowed me to connect my DDC singxer su-6 to the Wiim Ultra via USB, significantly improving the digital audio quality of the Wiim towards my Dynaudio focus 60XD and at the same time being able to use my Arendal 1723 2v subwoofer. As for functionality, the Wiim Ultra is truly unbeatable. I also used a node n130 lately (using the coaxial spdif output) and unfortunately I have to admit that the node sounds significantly more natural, more harmonics and in a more analog way. However, the node does not have the same functions and adjustment possibilities as the Ultra which also sounds more dynamic and loud. The blanket is short. The optimus would be a fusion between Bluesound and Wiim.
I also use digital out to active speakers (Dali Rubicon 6C), and I will today test the SMSL PO100 USB to digital to check if I notice any improvements.
I think your speakers are a notch better than mine though!