Hi sandrodg73. sorry for the late reply. I am a long time reader and first time poster on this forum. I figured I would get you some detail on my impressions of the M66...
I picked up an M66 on release day to try it out and have kept it as the primary and cherished preamp in my system ever since. I have it paired with the M23 power amp and it is great. For speakers, I am running B&W 706s3's and a pair of SVS 3000 micro subs. I have experimented on and off with DRAC and it is fun for tuning the sound but honestly I keep coming back to bypassing DRAC and appreciating the natural sound. My primary sources are a TEAC TN-5BB turntable with Ortofon 2M Black LVB cartridge for vinyl and Tidal connect for streaming. Really, really enjoying it for months now.
If you are into vinyl the internal phono preamp is good, at least speaking for the moving magnet configuration. I haven't tested the moving coil preamp settings yet. You can run the phono input in full analog mode or allow it to pass thru the digital processor... Both sound great, but I am surprised to admit I like the digital processed phono configuration a little more.
Streaming with Tidal sounds phenomenal as well. Super crisp, clean and clear with my setup, from the top to bottom. There is an interesting filter called DDH (Digital Dynamic Headroom) that has a subtle effect mostly on percussion in my experience. It is stated in the documentation to help smooth some digital artifacts and aid in making instruments sound more natural. Like I said, it is subtle but useful.
Bells and whistles aside, the system sounds great in my setup and is very easy to use after a mild learning curve. The BluOS app is solid and pretty much the hub for all the adjustments, steaming, volume controls, etc.
DRAC live is a separate software to get your calibration for EQ curves and such. There is a steeper learning curve to get the most out of DRAC and the software, but I got it figured out with a little help from google and youtube. As stated earlier, I am very happy with the sound of my system with DRAC EQs bypassed.