slbenz,
I have a C-1 which I use it with an Emotiva ERC-2 cdp and RPA-1 power amp. I've gone through my C-1 thanks to encouragement from BillD and other members here. Mine has the BillD mods as well as all 1% metal film resistors installed. I really love the way it sounds. It replaced an Emotiva USP-1 which I was extremely happy with. The major issue I have with the USP-1 is that it does not have a true tape loop. Huge downfall since I use a DBX 231 eq. I still use a cassette deck as well so having two "true" tape loops is essential in my setup
The USP-1 was the best sounding preamp I've owned to date. But since I modded my C-1 they are sonically equal to my ears. But, as I stated, the C-1 gives me much more flexibility.
I'll be waiting your impressions on the M-1.0 as well.