I would not say the M3 is dark. It is about dead neutral. That being said, it is all relative and you need to take into account system matching and where you are coming from. If your point of reference is Chord then yes, Bricasti will seem dark. If your point of reference is Aqua, then it might seem bright. It is relative but when you consider the range in terms of output, Bricasti is middling and about neutral.
regarding feeding an M1 SE with network card, your best option is a server with a direct Ethernet connection. The Antipodes S40 or K41 are perfect examples of how best to do this. I have used a K40 previously and it was a big step up from my Nucleus+. I do think a part of that is the direct connection and the signal not passing through my router where it is with the Nucleus+.