In my opinion, there is a very, very large difference between what I consider to be all around "good" bass and everything below it.
To me, "good" bass starts at $500 (plus shipping
) with the Rythmik FV12. That is the least expensive subwoofer out there that manages to have no obvious weaknesses. It is a very linear and accurate sub. It offers good transient response (stops and starts, which are what create "fast" or "tight" sounding bass). It has good extension, offering flat response down to about 23 or 24Hz with very useable output at 20Hz (about -3dB). And while it cannot match the sheer output of larger and more expensive subwoofers, it WILL happily play as loud as it possibly can, and then politely refuse to play any louder. Rythmik has engineered very good limiters, filters and compressors so that the sub will never damage itself, bottom out or even so much as produce very high distortion. So you can literally crank the volume as loud as it will go. The Rythmik might refuse to play as loud as you would like, but unlike many other subwoofers, it will not damage itself or even so much as sound bad!
Below the FV12, you will only find subwoofers that have some sort of obvious compromise - and perhaps several compromises. The HSU STF-2 is a very good subwoofer overall at about $350 (plus shipping), but it can't match the deep extension of the FV12 - instead, tapping out at around 25Hz with a gradual downward slope starting up just above 30Hz. So I have no beef at all with the STF-2, but it does have an obvious compromise. In pretty much all other important areas of bass reproduction though, the STF-2 is a champ, and an excellent choice for music, since very little music plays lower than 30Hz.
Now, the other thing to consider is that anywhere the air CAN move, the air WILL move. A subwoofer cannot "know" that only a certain portion of an open space is considered the "theater area". A subwoofer will simply try to pressurize the entire available volume of air. So you have to consider any and all areas where there are openings from your "theater area" into those other areas as all being one, big "room" so far as the subwoofer is concerned.
That said, soundwaves still get weaker and weaker the farther they travel, so you can still achieve louder bass at your seat vs. in the kitchen by positioning the subwoofer closer to your seat. The bass will still travel to any and all open areas, but it will be louder the closer you are to the subwoofer, so careful placement can still help