Being well familiar with Arcam gear having owned several Arcam components and currently using an Arcam AVR….
I think it will be difficult to hear the difference that the qutest will bring. Arcam already has a warm robust sound signature so it is already warming the sound signature from your blusound node.
your wife is probably spot on that it makes the music sound bigger as that would easily be the effect of the qutest in an Arcam system.
to help bring out the differences more for the better qutest I would look to upgrading cables in your audio system, interconnects and speaker cables included. Arcam has enough resolution to benefit from getting better cables.
I love the Arcam sound for my surround sound system. Warm clear properly weighty midrange sound without added high frequency hype or sizzle and doesn’t have one dimensional bass like most AVRs out there.
I owned a Qutest as well for some time and know that it is a good dac still in its price range.