Product Showcase - Interior

And there is that second compartment I've mentioned a couple of times now. As you can see, the 680X is equipped with mounting trays in the back as well as space to house the power supply. 

So, the Lighting Node PRO device to the left is basically a LED hub, it has the RGB LEDs from the fans connected to it. There are actually six connectors, so you could add another three LL120 RGB (or other) fans if you'd like to do so. The hub connects to the control unit that, on its end, needs to be connected to an internal USB header on your motherboard. Then install the latest version of ICUE and you are good to go. 
  

The photo turned out a bit too dark, but to the upper right, you can mount three HDDs and you will also find four mounts for SSDs. The Lightning Node Pro is visible as well. 

At the bottom you can mount the power supply, really any length will fit. There's a handy retention clip here as well. The rest of the space can be used for cable management, and there's a lot of space for it!