You have not specified a price range for the subwoofer(s), so you will probably get the usual suggestions for the better-known subwoofers: REL, Velodyne, etc. Among the subs you should consider, include the Vandersteen 2Wq (or V2W if you are going to use the sub solely for home theater).
I recommend you audition the Vandersteen 2Wq sub, preferably in a stereo pair, for the following reasons:
1. the Dunlavy speakers are time and phase accurate, as are Vandersteens, so you will preserve this important aspect of your main speakers performance (the 2Wq has a 6-db, first order crossover);
2. the 2Wq crossover connects between the preamp and the power amp (whereas the V2W is driven from the LFE outputs on the pre/pro), so the subwoofer receives the signal from the power amp, thereby giving the entire system the characteristics of the main power amp;
3. the 2Wq allows you to adjust the "Q" (damping) characteristics, thereby making it easier to tailor the output to match your room and main speakers;
4. the 2Wq represents an excellent value (price vs. performance).
I recommend you audition the Vandersteen 2Wq sub, preferably in a stereo pair, for the following reasons:
1. the Dunlavy speakers are time and phase accurate, as are Vandersteens, so you will preserve this important aspect of your main speakers performance (the 2Wq has a 6-db, first order crossover);
2. the 2Wq crossover connects between the preamp and the power amp (whereas the V2W is driven from the LFE outputs on the pre/pro), so the subwoofer receives the signal from the power amp, thereby giving the entire system the characteristics of the main power amp;
3. the 2Wq allows you to adjust the "Q" (damping) characteristics, thereby making it easier to tailor the output to match your room and main speakers;
4. the 2Wq represents an excellent value (price vs. performance).