Thanks for all of your insight!

I was looking around at subs... I liked what I saw at the SVS site the best. Does anybody know if there is a real big quality difference between these?

SVS Box Subs
PB10-ISD ($430)
PB12-ISD ($600)

I was also looking at the Dayton 10" 100 Watt Sub at partsexpress.com which is $220.

Which of these subs would be best for a 15x25ft room, value wise?