Is this number including an extra ~2-4 inches for the power cable clearance at the rear? In your new case and most others, power and cooling at the rear requires a few inches of clearance in addition the depth of the case itself, otherwise the power cable cant physically fit. I've made this mistake before, with a wall mount rack those extra few inches matter in a way it doesn't for a free standing one, where cables can extend beyond rear edge of the rack without meeting a wall.
EDIT: The box Jeff has used is one of the few I've seen that might actually work well in a wall rack, if you can live with an mATX form factor motherboard in your build, at ~9 inches, which leaves enough room for power and air at rear.
If you want a Linus Tech Tips style gaming rig or mid/fullsize tower build in a rack, I still think you might need to go free-standing most of the time.
EDIT: The box Jeff has used is one of the few I've seen that might actually work well in a wall rack, if you can live with an mATX form factor motherboard in your build, at ~9 inches, which leaves enough room for power and air at rear.
If you want a Linus Tech Tips style gaming rig or mid/fullsize tower build in a rack, I still think you might need to go free-standing most of the time.