sub for spica tc50

Finally got a pr of spicas for the bedroom would like a small sub just to bring them down a little any suggestions.
I had the TC-50's with the Spics Servo Subwoofer years ago...great combo.

I suggest a look at the Gallo TR-1.
Kinergetics made a pair of subs specifically for this application, as well as stands to hold both them and the Spicas, and amps/crossovers to drive the subs. It was popular in some very high-end audio dealerships 20+ years ago.

I heard many people criticize it, but personally, I absolutely LOVED the package. Not sure why I didn't actually go through with the purchase myself at the time, but I think I was chasing a pair of Legacys - which after finally hearing them at the same dealership, felt they absolutely paled in comparison to the Spica/Kinergetics.
I recommend looking into REL subwoofers.