Where is your subwoofer placed in your room? The cheapest option for getting more bass would be to place your single sub in the corner or near the corner furthest from other openings into other rooms.
Also, it sounds like your room is very reflective. One way to tighten things up is to put a throw rug or carpet piece between you and your speakers. Or, adding bass treatements and panels to your room makes a great difference in flattening out your room response in the lower frequencies.
As Adrian mentioned, adding additional subs in your room, normally across on the opposite wall can make a great improvement.
