How much of a difference in the sound of just the subs? or the whole system? Until you get into the higher end EQ's, they usually only have a band or two that are even in the range subs play. 1/3 octaves allow you to tune the sub bdans decently. Sound processors like the alpine 701 have multiple bands in the sub range, plus parametric bands for th subs, which allows for -alot- of adjustment, but they are pretty expensive. If you want an Eeq JUST for your subs (like if your other speakers are not pushed with an external amp), Id say its not worth it.