There are many things that effect how good a bass you can get, from the room its in, to the sub enclosure, driver size, reverb, ported or sealed. I have found most store bought subs (like Klipsch to be just average) I would look at frequency response graphs to see how flat and linear the bass is before it falls like a rock, which will determine how good it is. Take my DefTech Prosub 800 it drops right at 38Hz so I use it only to 40Hz, while my SVS handles all the real low bass down to 20Hz.