Seems like these kind of builds are getting really popular! Take a look at my build if you need some ideas: https://forum.level1techs.com/t/build-log-silent-night-my-own-take-on-quiet-and-power-efficient-nas
tl;dr AsRock N100M, single stick 32GB 3200MHz, 7L case, 6x4TB SSDs, external power brick.