down-firing

Got my Tempest-X2 in (thanks Kevin!) and am working through building my box which has the driver firing down into the floor. I have 5lbs of polyfill per the 1lb - 1^ft suggestion. Do you guys just throw it in there and let it settle on the back of the driver? Do I need to worry about it...

I'm seeking recommendations for a second budget-priced SW, to round out my 7.1 system in a 3900cf family room. Main constraint was "no speakers, no wires" showing, so main components (Large Advents, 8" Yamaha SW, BIC center channel, Sony STRDG920 and accessories) are all hidden behind...