Finest subwoofer for music under $1,000?

As suggested REL is unbeatable when it comes to music and seamless integration. REL matches with any speaker you have provided you hook them up to the power amp output with your speakers ( kind of biwire which on the sub is called hi level). You run your main speakers full range and get the sub to mate with it, which means no nasty crossover glitches or distortion is introduced in the signal chain.

Strata III is a sealead unit which is even easier to blend with the room and speakers. Strata II was ported. All the models above Strata are ported. If you have a small to medium room sealed is better.

vmps -take a look

Its a stretch but for around 1K(used-usually abot 1200.00) you can get a Martin Logan Depth. It integrates with 2 channel as good as I've ever heard,and for surround its incredible.

paradigm's new pw-2100 for $730 retail is very good...nice 10" driver w/ 400w amp.

Infinity Alpha 1200S sub. My friend is using this on his Canton monitors. This sub lists for like 750. It sounds great on music
It uses that Rabos technology which is an equalizer to make sure the sub blends in perfectly to the speakers. It uses a Ceramic alluminum 12 inch woofer and a 500 watt amp. Here's a pic of it. http://www.infinitysystems.com/homeaudio/images/products_large/ALPHA1200SBK.jpg