@rsf507
M12 is only worth it if you have Bricasti amps. Its built-in that is not bypassable pre did not match well with other amps I tried.
If you are set on Bricasti please get the M21 instead. At that level a separate pre is a must.
The Nagra tube DAC is something different, everything I was wanting in my system suddenly was there, and I am no longer scouring audio sites for my next purchase. There was soul and there was resolution, violins for the first time sounded just right.
Is it worth 2X the price?
Yes, because your search for a DAC ends. Tube DACs are where it's at, IMO. But do try cheaper ones like Brinkmann Nyquist dac before jumping to the Nagra. I didn't do that, but should have, it's the only regret I have. Also please note, Nagra doesn't sound tubey at all, you wouldn't know there were tubes if it weren't for the name.