The twin 500 will allow for a smoother bass response throught out the room( this is room dependent as grunt had no help from dual subs) while the EP800 should allow for deeper LFE to be played back adding more feel to the effects. I thnk most would like smoother overall response over the deeper playback of the 800 but I think I would go for the single 800 to get the deeper LFE playback for movies as I like my sub(PB13 Ultra) when tuned at ~15hz response over it tuned at 20hz.


Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70