Too much bass in room with sub?

In a room 20 x it wise to opt for a musical sub that goes to 20hz, 30hz,etc...or does it matter? I am trying to eliminate exaggerated there a scientific equation to caluculate(dont laugh!)...thanks...
A well-designed subwoofer should give you superb bass down to 20Hz without bloat in such a room. It will have a falling frequency response starting around 35Hz that would be flattened out by room gain. My REL Storm III, for example, doesn't boom at all in typical apartment living rooms and it improves practically any speaker.
The exaggerated bass is probably in the 50-100hz. range, you should be able to smooth it out a little through sub placement and x-over point setting. You will need at the very least...spl meter and test cd along with pencil and paper to make some freq. responce charts to plot your progress.

The above will give you an idea of what problems are being caused by speaker/sub placement and what problems are being caused by the room it's self. Solve as many of the room problems as you can with bass traps in at least the corners.

Subs that don't go down into the 20-30hz. range are not subs, subwoofer range is from around 60hz down to loss of the ear being able to hear the freq. (20hz. will do).

Another common problem is that many people set their sub level by ear..this causes them to turn it up until they can hear it, of course...once you can hear's set to loud.