If you can find a Bag End Infrasub-18 for under $1,000 used, grab it. It is extremely fast, tight, and musical - not to mention that it is flat down to 8 cycles. You will hear and feel bass that you did not know existed before.
Best Sub for Music, Under $1000
I currently use a Revel B15 to fill out the low end on my Tyler Acoustic Monitors. This weekend we put the B15 into our home theater system and realized that it's extremely low frequency response was being underutilized in the two channel music system, so I am in the market for a great sub for music only - the catch is that I have only $1000 to spend - used would be fine, but I would prefere a transferrable warranty. I am considering going with the Tyler Acoustic Taylo Sub, but have not heard anything about it one way or another. Thanks.