Note that if you want to put an mATX board in the Cerberus-X there is nothing to physically block it: the problem is the standoffs are permanent installs (due to anchoring directly in the backplate) and for an ATX board to fit, there are three standoffs not present. These three standoffs (B,R and S) would normally support the entire lower half of an mATX board, so installing one means the expansion slot section is unsupported. If you are willing to install your own standoffs (self-adhesive plastic standoffs are ugly but easy to apply) you can use an mATX board in Cerberus-X.