I have to disagree Jman, I think you get what you pay for with PSA, Now I know a couple guys on here like them and swear by their value, I have recently heard an XS15 and a XV30, neither impressed me, and although Shady is known for stirring the pile a little (sorry) I have to agree the picture of that sub with the tiny magnet doesn't do them any favors in the "get what you pay for" argument, I know a few guys on here recommend them to people and I cringe when I see it, there is a reason HSU owners swear by their subs and others swear at their subs after they hear the HSU and see the price...
Dave bought an XV30 and I dont remember how much it was but I was NOT impressed with it, and neither was he, he had heard my vtf2 a bunch of times and thought the 30 was going to smash his expectations, after we moved it around and played with the settings, I called the rep from HSU I have dealt with and he {while being respectful and not bashing the competition} told Dave {on speaker phone so I heard the entire conversation for myself}, "I will send you a VTF3 dual drive, if you don't like it Ill pay for return shipping and buy you dinner". The price was basically the same and although I wasn't there when they were delivered, his wife said after plugging them in, the first thing he did was box up that coffee table sub and push it to the garage... I have since watched movies at his house and can say for the money, that is one heck of a setup, if you need more than that you must have a 900sq ft theater because his room is huge, and he has them sub amps gain set below the half way point...
I have recommended HSU to a lot of people, and I have gotten countless thank you PMs and emails after the product arrives. I have heard almost all of their products, ULS15, VTF15, VTF3 {own one} VTF2 {own one}, STF1 and 2 {own one}, and I own other subs too, and have owned others and have demoed SVS and a couple other companies, its a hobby, and IMO HSU is the way to go, their CS is top notch, their products are awesome well designed, well put together fit and finish it top grade, tune ability ect is all thought of a head of time, their lineup covers 90% of the bases, nice musical subs, big theater subs, small budget subs, ect.. Its all there... In my living room the sub I use most is the vtf2, I have toyed with building some of my own, but that sub over powers my good sized living room with ease, they jerk in me wants to get something bigger and two of them, but then the other side of me says, don't be a jerk the 12" is too much for you as it is....
So anyway thats enough from me, Budget is the most important factor, if money was no object, JL audio, Funk, Ect would be awesome to own, but when you are building a theater and want good sound for half price we have to search around and ask others what they think, just make sure you get a sub that you can demo and return, if you have the time and interest get a couple, but as for companies I would be looking into it would be HSU and SVS, and in my experience the HSU will be the permanent fixture in your home...