But I learned much from this project. I am happy it works and don't look back on the outside. If you wondered why it's called "p5yk0station2", the "first" p5yk0station was a Mini-ITX-PC inside the PS1 Case, with use of the original switches, but it failed with heat problems 
Next project will be something inside a Commodore64 case with use of it's keyboard. But this time, i plan first, then build 
@Substring i used an usb converter that already recognised 2 gamepads on the first startup. Even without pads plugged in.
I didn't use the original power switch in this build, because there was not enough space for it left. Maybe next time 
PS1 Case including:
RasPi3
160GB HDD
Adapter for PlayStation gamepads (manually soldered)
GPIO ON/OFF switch
Hardware ON/OFF switch
3.5A / 5V supply
LED stripe for glow-effect
Its not pretty because I just pushed inside what i needed without thinking, but I learned for future projects
You can change the Pi OS-card without disassembling the case.
Like I said, in the inside it looks so bad because i didn't think while pulling all together.
But I hope you like it