No matter what sub you go with, proper setup and addressing room acoustics are every bit as important as, if not more than, the differences between the different subwoofer models because of how rooms interact with low frequencies. Just dropping a subwoofer into the corner with no calibration will likely give you "one-note" bass. It'll be loud and boomy, but far from accurate, full sounding, and/or listenable.

Ideally, the subwoofer takes over where you main speakers leave off, and handles only the lowest of the low frequencies. You should not know it's there; only if you turn it off should you notice that it's missing. The thing about subwoofers is that your room will likely induce at least one severe peak at a specific frequency. It's those peaks that cause subwoofers to sound boomy. You actually want to reduce the peakiness so that you can turn the subwoofer level higher and let the bass sound fuller. Boomy bass gives you emphasis at those peaks, but makes the rest of the bass range sound very lean and wimpy. (kind of like listening to an acoustic bass where you sorta hear it until the musician hits one particular note and it sounds loud enough to ring your head)

If addition to getting a subwoofer, you should also invest in a SPL meter and a test disc of some kind. At the very least, you want to make sure that the overall level is correct. Ideally, you would use the test tones to identify where potential problem frequencies occur. If you find any, then either a parametric equalizer and/or room treatments (plenty of DIY solutions out there that you can build out of simple building materials and a glue gun) will be needed to optimize the sound.

This may be a bit advanced, but optimizing the equipment that you have will save you money in the long run because a proper setup typically goes a longer way towards improving your sound quality than swapping out equipment.