E-ATX is not an official standard, but only means wider than ATX and at most as wide as SSI-EEB. The WRX80E-SAGE corresponds to SSI-EEB and, with a little modification, also officially fits into a Dark Base Pro 900 (Rev 2). BeQuiet has explicitly confirmed compatibility in their support forum. I myself have a Dark Base 900 Rev and have adapted it accordingly on a trial basis: Move the mainboard bracket down one step and mirror the drive cage (rotate 180 degrees). After that, there are corresponding threads in the drive cage for the standoffs on the far right for SSI-EEB boards!

Asus works with its own standard for E-ATX (like all others) The motherboard can only be installed in SSI.EEB size cases. (Lian Li OD11 XL and Dark Base..this is not possible! Possibly an extra part can be bought for Lian Li that enables the installation).

Thank you very much for pointing this out. We have not found any information that the details are incorrect, but we have passed it on internally for verification as a precaution.