the back row is on a riser, I assume one unit would attach to the riser to rattle the back row. I just installed Dricor subflooring which is a floating subfloor to let the basement concrete breath and evaporate any moisture. It is a toungue and groove system, figured that the 2nd buttkicker could be installed to the flooring behind the front row. I've hear people say their sub performance dramatically improved once installing Dricor, versus over concrete and carpet.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85