I bought a SVS 20-39PCi a couple of months ago and it is flat out amazing. It goes lower than anything I have ever heard. I have knocked pictures off the wall with it at high volumes. CD's and DVD's are a new experience. I am hearing and feeling things that I did not know exist.

The two numbers are its frequency range and height. Mine plays flat to 20 Htz and is 39" tall. Their other cylinder models are 25-31 and 16-46.

Mine was $599 plus shipping and I consider that a bargain.

Regards to HSU subs too. I cannot recommend because I have not heard one personally, but from what I understand, they produce a great sound as well. Either of these two brands (along with adire audio) are widely considered the best "bang for you buck" subs in production today.