Over at AVS, for those who haven't seen it, there is a great writeup by some users of about half a dozen subs that are in the 15"-18" size range. Hopefully everyone has looked at that writeup already, but for about, and typicall less, than $1,000 there is some great product out there.
Yeah, it would be nice to see how those products stacked up against the top tier retail/custom install models such as the Velodynes, JL, and other models. But, I'm pretty sold on Epik since reading those reviews. I've installed two for clients in the last month.