I'd place the 4 fans blowing up at the top of the rack and dress the room-facing side with the optional panel and leave the wall side bare. Assuming you can space out your gear place comp coolers from MA or CC on the gear to blow across the chassis and out the rack either to the back or sides. That AD-8 keeps itself cool and it sounds like you just need to kill a rack space or two on a unit to cool your amp. I wouldn't close up that rack since you have a nice closet space to dissipate heat. This is also assuming that you're pulling air out of the room in the space above the rack.