I got both my Rythmik D15SE subs for $2,200.
I would check out the Audioholics Subwoofer showdown/reviews.
I read the Audioholics reviews, then the AVS forum on the Rythmik subs, and I was sold.
What sold me on the Rythmik subwoofers is they have excellent damping capability, Q = 0.5. Actually on the Rythmik website, they claim an effective Q value of 0.3, which is absolutely exceptional. They are extremely tight.
The Rythmik are great subwoofers.
I'm sure there are other great subwoofers out there.