Thanks for the reply rnatalli. I looked at the Rythmic and it looked nice but is not available in a real wood finish. Maybe I'm not seeing the forest through the trees but the real wood thing is an important factor. I like the looks of the HSU subs so I will check out the MK3. Sound quality is important to me but price is as well. However, if the SQ of the MK3 is going to be as good or better than the rest it seems like a win-win since it is would still be less expensive than the other options. So, I think I am leaning towards the HSU but still open to suggestions.
One thing about the MK3. The driver is on the side of the unit. That is fine with me but will it matter if that side of the unit is facing a wall? One of the possible positions in my room would have the speaker in a corner of an alcove and that side would be about six inches away from a wall. That is one of the reasons I was considering the VTF-2 as it has a downward facing driver. Also, when you factor in shipping the VTF-2 comes in at almost $200 less than the VTF-3. Not a big enough amount if there would be a big difference but big enough to not spend it if there won't be that big of a difference.
Matt
The direction the driver is facing doesn't matter too much, as long as there is a little bit of room for the driver to move air in. Six inches ought to do fine. Make sure the ports have some space between the wall also.
The PB12 Plus will almost certainly be capable of more output, and probably extends a little bit deeper than the Hsu subs. The Hsu subwoofers are very powerful though, more than enough for most people. In the wood veneers, they are attractive enough to double as an endtable, or something furniture-esque.
Either sub will rock, but I wouldn't place the sub in a closet if I could help it. Placement is very important to get the most out of your sub, and a poorly placed sub can really hurt the sound.
From what I have read, the VTF3 has much better deep bass performance than the VTF2, which might or might not make a difference, depending on what you listen to. What will primarily take advantage of that is modern action and science fiction movies, especially blu-rays. If you are using this to supplement TV shows and music, you might not gain a whole lot with the VTF3, except for a bit of overhead when you want to rock it, but if you have a home theater and you want to feel those deep rumbling sounds as well as hear them, go for the VTF3. It has a nearly flat frequency response to 16 hertz in max extension mode, whereas the VTF2 doesn't quite go so low as easily.