Well I figured that my 50W RMS 10 inch polk audio sub hits 100.2 decibels on the norm, if i got a sub that basically would multiply the Sd of the 10 by about 4 and a half, that shit would slam regardless. Of course I would have to power it correctly or it would sound lame. My goal is to get louder bass on songs like hard in the paint or bass I love you. Because anyone can have a sub that slaps at 100Hz but I really like that feeling of a 25-40HZ soundwave being blasted in a room. The feeling is undescribable. My dad has a B52 matrix 1000 with the 15 inch driver and that rattles the house. So I feel like 1 upping his system with a slightly overpowered 21!