I would strongly recommend against stacking anything directly on top of the 7100. The M200 monoblocks are designed to be stacked (both structurally and from a heat rejection standpoint), but the 7100 and Outlaw's other multichannel amps really want a couple inches clear above them for cooling. I got by with as little as an inch and a quarter with my 750 in our old equipment rack, but that rack was fully open in the front and back and the 750 was at the bottom of the rack (so no heat was rising from equipment below it).

Like the 770 and 755, the 7100 does not use a cooling fan - the amp channels are equipped with large heat sinks and the top of the amp is dedicated to ventilation openings for heat rejection from those sinks.