Subwoofer for "seamless" integration with Zu Druid


I've had a pair of Zu Druid Mk-iv's for about 3 months now. I'm really digging them, but miss the lower octaves. I don't know much about subwoofer design or manufacturers. Anything that would give me solid response down to 30hz (or even lower without sacrificing speed) but still be fast and tight.

What is the best design for integrating into speakers such as the Zu's (sealed, ported, with passive driver, etc.) and what brands/models should I be looking at? I'd like to spend no more than $1,000.

The REL's are reviewed well, and the Zu Method and Mini Method seem an obvious choice, but aren't manufactured anymore and are scarce on audiogon.
fargel
My experience may not be very relevant since my Druids are somewhat modified. Anyway, I have had great success using two JL Fathom f110 with my Druids. Features such as inbuilt auto dsp, phase, and roll-off options provided by these subs makes it fairly easy to achieve good integration. I use two because I am a bass-freak but one should be adequate and can be acquired used at your budget.
I have a pair of Zu Essence speakers with the upgraded nanotech drivers. I supplement my bass with a Zu Mini Method subwoofer. The combination is fantastic. The Mini Method is an amazing little subwoofer. It integrates seamlessly with my Essence speakers, no compromise at all. Closed port subwoofers are incredibly fast, only sound boomy if the setup is entirely awry, and are a cinch to integrate with a copasetic set of speakers. I know that Zu Subwoofers rarely come up on the used market, but, if i were you, I would be patient and keep my eyes peeled for one to come up for sale. Someone sold a Zu Method, here on Audiogon, a couple of weeks ago and Zu Promos just sold a Mini Method on Ebay three days ago. So, even if they are somewhat rare, they still show up for sale at times.

Good luck,

Ivan
I own the DruidV and a pair of Zu Undertone subwoofers. It is an excellent combination. The integration of the subwoofers is subtle but very noticeable when they are turned off. It gets the sound down into the lower end. Talk with the folks at Zu.
You should definitely call Zu. They may have a few remaining Methods, etc available.