Your room is slightly larger than mine but I find that my 12" SVS SB-2000Pro does a fine job. Maybe not enough for a bass head like William
but it was a big improvement over the cheap Klipsch I had previously. If it's a rental and you're limited as too how loud you can play the system, the Paradigm X12 would still be a good performer. If you foresee yourself moving to a larger space in the future, then the X15 would be a longer term investment.