Which DAC as a preamp?

Hi folks...I am looking for opinions regarding DACs to use as a digital pre-amp to drive my red dragon monoblocks. I am considering Audiolab MDAC plus, Musical Fidelity M6s DAC, NAD C-510, or the Audio Alchemy DDP-1.    Any thoughts as to which would be the best pick?
just never worked for me without a pre. that said the mytek manhattan has an analog pre and is a very good dac. 
@shadorne , @transience, I too expected my very mellow balanced tube preamp to tame the highly analytical M6S for a perfect match. On SOME recordings -- notably those originally analog mastered -- it works splendidly despite subsequent remastering. (Example: Keith Olson's 1975 "Fleetwood Mac" eponymous album remastered in 2017). But on more recent, digitally mastered material with substantial high-frequency content, the M6S's 768 upsampling screams like a banshee, cackling right past the tubes when coupled with RCA-terminal coax. Have not yet tried using USB or optical (M6S has no AES input), but if those don't tame it, I've got serious trouble. 

Any hints? Maybe I will start a new thread if a different coupling doesn't help. 

RCA coax is intended for digital signals. I suggest to try the M6S RCA analog output with simple analog RCA cables.

I've not heard the DACs listed by the OP. I've found the Sonnet Morpheus to be excellent driving my ATC SCM100ASLT active speakers.
If you look for a fully featured preamp and top DAC, look at Antelope in the used market. Zodiac Gold or Platinum are hard to beat