I had a pair of early Velodynes. `I thought the accelerometer on the cone was a cool idea. In 10 years the surrounds rotted. I use one of them as an end table.
Au_lait, I would not plan on doing anything until you can do two subwoofers. One never works well given acoustic considerations. If you are serious about sound quality it will drive you nuts. If you just want to vibrate the floor for movies one sub will do the trick. It is always best to get the two subs at the same time as you want to be sure you get identical units. Stereo is always a function of symmetry.
Au_lait, I would not plan on doing anything until you can do two subwoofers. One never works well given acoustic considerations. If you are serious about sound quality it will drive you nuts. If you just want to vibrate the floor for movies one sub will do the trick. It is always best to get the two subs at the same time as you want to be sure you get identical units. Stereo is always a function of symmetry.