Boomy bass is mostly a problem with the way you setup the listening position within the room, rather than the build quality of the subwoofer (esp. if you are paying 350$+). Setup of the subwoofer, speakers, and listening position is so very important to prevent boomy bass issues. In fact, if even one of the 3 positions mentioned are compromised, you will most likely have boomy bass issues (or zero-bass issues).
If you watch any kind of action flicks, you will immediately notice the improvement. The explosions will just simply put a smile on your face and you won't exactly know why, but it is because the explosions are more realistic (as they have quite a bit of data below 30hz).
But, just make sure that you understand that setup of subwoofer, speakers, and listening position are all paramount. Any compromise to these things results in an overly-compromised sound.
For example, if couch is up against a wall - bad, boomy bass. If the couch is in the mid-point of the length axis of your room, the bass will be hollow and empty. If the couch is any even fraction of the length axis of the room, the bass will be hollow. (in a rectangular room, 0.30-0.45 of the length axis is a good start).
Also, if you are worried about imaging, the symmetry of what is to the left and right of the speakers makes the difference for this audible quality.
Bass builds up in corners, so a subwoofer in the corner of the room will energize all room modes while also gaining a free boost in loudness due to it being in a high-energy zone of the room. This can lead to muddy bass depending on what nulls are problematic at the listening position, where the crossover is centered, etc. Placement of subwoofers on midwall eliminates one of the 3 major room modes while careful crossover settings can eliminate the height-based room mode.