LOWS ARE 20-80 trust me, this is an optimum range for subwoofers.
80-500 is midbass territory please stop confusing stuff. 125hz-300hz is where you get instrumental and drum kicks and background midrange and 300-500 hz is male vocals which has nothing to do with bass comming from a subwoofer. For hard hitting bass, you have to put them in a proper box, as of now, the pre-made box you have will make everything sound like **** and wont get loud even if its the last subwoofer on earth. Kickers need a huge custom made box in order for them to get loud and sound good.
the range of hertz for subs mean jack shiet most of the times its not a measure of how much of a "WHOMP" a sub would give. power and enclosure determines your "whomp" factor.