What subwoofer for Joseph Audio RM25si

What subwoofer will fill out the sound from my Joseph Audio RM25si speakers (currently driven from an Anthem MCA-20 amp)? In addition to the usual considerations about sound quality, I have a couple of connectivity needs to meet: I want the subwoofer to have loop output with RCA connections, and to be able to turn it on and off with a 12 volt signal. (These specifications are so that I can continue to use the second set of outputs from my Aloia pre-amp into amplifiers that drive speakers in other parts of the house.) Suggestions welcome. Thanks.
I can only speak about what I use. The Velodyne DD series will accomplish what you want to do. They have RCA out and will turn on and off based on whether or not a signal is being received. Other features are a remote control and DSP room equalization. I use the DD-10 in a fairly large/open room. Happy listening.
I agree wih Cio52. We have had the best luck with integrating the Velodyne DD series subs with the Joseph Audio speakers.
Without knowing your budget, the 'darling' sub right now, is the JL Audio Subs.
A friend just purchased a pair, and they are about as musical as any sub, which is of that size, and highly equalized, can possibly be. Powerful, musical and fast.
They are quite good.
Good luck,

I use Velodyne DD-15 with my RM25si. The digital equalizer of the sub is useful in a small room like mine(16X11X9). Joseph claims a flat response down to 30Hz for the RM25si but I measure a sharp rolloff below 40Hz. That said, a lot of music doesn't need the sub. There isn't much below 40 in jazz or rock; there's not a noticeable difference for most music if I turn the sub off. I can't comment on your connectivity issues.