I own a Focal Aria 926 and STA-9/DAC-9 combo. I have recently purchased a Lumin D1 to try out its DAC and player.
Ends up I sold the Lumin D1 after shortly because I found it sounds very similar to DAC-9.
I compared "Macbook -> USB -> DAC-9 -> XLR -> STA-9" and "Lumin D1 -> RCA -> DAC-9 -> XLR -> STA-9" setup.
Tonally two components is almost the same, I don't know is it because I hook Lumin D1 to DAC-9. It is difficult to identify two componenets in non-blind AB testing when listen a short clip.
If I listen to Lumin for a longer period time, I do found it easier to listen to, it has more details, better image, less hash and more enjoyable. I would say D1 gives me about 10% improvement to my system. Given the Lumin D1 cost more than the DAC-9, I decided not to keep this unit and stick with DAC-9.
(Hey, they blend in together nicely!)
I recently discovered that connecting STA-9 and DAC-9 with RCA actually sound smoother than XLR.
XLR connection is louder than RCA by 1.5db, has higher quality on everything, except it might sound hash and loud (to my taste) on some music. (like POP)
I am happy to find out that I have option to switch between two different sound in my amp.