Hey tonnesen & rja,
1) If your system is single ended and you don’t have any desire to eliminate your preamplifier, then the Audio Mirror DAC saves you a lot of money and still competes regarding it’s overall sonic performance.
2) I have heard the Sonnet DAC in another system and agree, it’s an excellent piece of gear. Enjoy your M3, it’s another great sounding DAC along with providing a reference level volume control. It’s also the first Sigma Delta single chip DAC that I would want to own because of its musicality. Hope you feel the upswing in price was worth it regarding your purchase of the M3 in your system’s performance. I have two more DACs to write reviews on, the Mhdt lab’s Balanced Pagoda and the Audio Note (England) Balanced 3.1, so I’m still continuing the process of reviewing DACs at different price points.