@audphile1 So full disclosure, I used to own the M1 about 8-9 years ago when I was a headphone user. I really loved the DAC at the, especially with the HD600's connected directly to the balanced out's. Because of my fond memory of it, I wanted to audition it again. With this time, I did play with all the filters but the one I settled on was minimum 4. With that said, I did find the filters offered a generally subtle difference, personally, and the M1 sounds like the M1 regardless of filter setting.
@mclinnguy Yes, I did end up with a more expensive DAC but the PS Audio was also not the cheapest on my list. Both the ANK and the T+A DAC200 were less money. The reason I auditioned the PSA was that the dealer that sold me my speakers offered it to as they felt it offers excellent value and was well worth a listen.
And you are correct, I noted the error about the PB names after I posted but I couldn't edit my post. The PBD unit I first saw/demo'd was the MPS-8 (DAC/Player/Streamer in 1 box) as they did not have a MPD-8 on hand. I did my auditioning using the MPS-8. The unit I bought is the MPD-8 (DAC only) as I did not want the CD player or streaming functionality. According to Andreas Koch, who was very kind in answering all my questions, was very clear that as a DAC only the MPD-8 is the better choice, though the units are very close sounding. Having heard both, I would agree.