The shelf that separates the amp area from the TV area has 6 holes routed in it that are each 1 1/2" x 3". 3 of these holes are in the amp area and the other three are in the DVD/DirecTV receiver area (currently empty). The holes serve as both wire ways and ventilation. There are two cooling fans on the very top of the TV cabinet which extract heated air from the entire cabinet.
The cabinets were designed around the speakers for that reason. The speakers have 1/4" rubber bumpers on their bottoms allowing for 1/4" clearance on each side, top, and bottom.