Network Storage build help

I am wanting to build some sort of network storage device. I am graduating from a qnap nas and thought I new what I wanted but in doing research there is just so many ways to do it. The main things I want out of this is lots of space for expansion(around 20 drives) and very fast transfer speeds. I'm set up for any format of build, I can put the setup where I work so I dont have to worry about noise, space, or power consumption. Any suggestions are appreciated, Thanks