Velodyne? NSU?....Which sub?  

Small correction: it is Hsu Research. Nsu is how it sounds when someone has a stuffy nose

For about 6yrs now the VTF-2 has given me sheer trouble free awesome sound quality. It been a total pleasure owning the little Hsu. A lot of subs say they can do what the little VTF-2 can do but unless your DIY almost none can beat it. Tom Nousaine in Sound & Vision measured 109.7 dB from 25 to 62 Hz with under 10% total harmonic distortion. Reviewer Peter Aczel measured 0.63% distortion at 100 dB! 25 Hz to 100 Hz ± 2 dB frequency response. For under $500 its a great buy and best thing is it can play music which most can not because of the orientation to being just a special effects boom box.

Ddavidson

The VTF-2 is currently on sale at the Hsu website for about $450. If you can stretch your budget beyond the 300 bucks you stated, you'd probably be very pleased with that or the $399 STF-2. Of course, the STF-1 is only $299, but that extra hundred gets you quite a bit more.