The thing about subs is that as you go lower into the bass range, the room starts to dominate what you hear. That's why demo room listenings IMO are practically useless unless all of your listenings were done in the same room and calibrated to the same settings. If you did your listenings in different rooms, then they are not comparable because each room has a different set of acoustical issues and unless you check and calibrate the unit yourself, you have no idea what the settings are being used at any give time (level? crossover frequency? phase? high pass or low pass?).

Subwoofers will vary a lot as you move them from room to room, and any room induced issues that you encounter in your setup will affect any sub the same way. That's why a lot of people on this board who use subs will tell you how much of a challenge it is to get a subwoofer to sound right and how important the setup, placement, and room corrections are. Whatever sub you go with, I suggest that you also buy at least a SPL meter and test disc so that you can do in-room response measurements and see if there are any large peaks or nulls that you need to correct. Correcting room induced problems can be done by repositioning the sub, installing room treatments such as bass traps, or hooking up a parametric equalizer. I use a parametric EQ with my sub, and IMO it's an indispensible tool. Easily the best $120 you can spend on your system.

As far as subs go, the PS series I believe uses a modified bandpass design where the driver is enclosed and the bass propagates from one chamber to the next. You can get deep bass with this kind of design, but subjectively it might not sound as tight as a ported or sealed sub. The PW series I have heard before and they have a lot of authority with the bass (keep in mind this was a treated demo room where I heard it).

Sealed subs like the B&Ws are more forgiving by design. Easier to design and build, and easier to place. But, they are less efficient, can't go as loud, and are more prone to distorting as the bass goes to the lower limit of the driver. However, they generally have quicker transient response, which leads to the perception that they sound "tighter", and they have a more gradual rolloff at the low end, which is why a lot of people subjectively feel that they sound more "musical". In a small to medium sized room, you will get room gain at the low end and with the more gradual roll off at the low end, you could wind up with more bass extension than the specs tell you by going with a sealed sub. If you're looking to go music-only with your system, then a sealed sub should definitely be one of the choices that you consider. (If you want to hear a good one, Paradigm's Servo-15 is a great example of what a sealed sub can do, although it's quite expensive)

Aside from B&W, Atlantic Technology, Adire Audio, Onix Rocket, and Acoustic Visions all make sealed subs in your price range. I posted some info on the new Acoustic Visions MRS-10 yesterday. It's a downfiring, sealed sub with a 10" driver that can move a lot of air. Here's the link.

New $450 Sealed Subwoofer Option