Pairing a sub with A/D/S L1290s

Hi guys,

I'm looking for a sub to sit with my A/D/S L1290s. I found their PB-1500 Powered sub that comes with their C-1500 "Bass System Control" going for $850... but not so sure as that's more than the towers cost me to begin with. I do like the idea of staying with that family. Any recommendations of a (perhaps vintage) sub that might work well here?

I paired my 1290/2's with a Velodyne F1500R for 25 years until it blew itself apart a month ago. You don't need to stay in the "family" to get good results. My 1590/2's also are using the same sub model from Velodyne. I have also owned the PB-1500 setup, but it couldn't compare with the Velodyne's. The $850 price is way too high, IMHO. 
I had a pair of early Velodynes. `I thought the accelerometer on the cone was a cool idea. In 10 years the surrounds rotted. I use one of them as an end table. 
Au_lait, I would not plan on doing anything until you can do two subwoofers. One never works well given acoustic considerations. If you are serious about sound quality it will drive you nuts. If you just want to vibrate the floor for movies one sub will do the trick. It is always best to get the two subs at the same time as you want to be sure you get identical units. Stereo is always a function of symmetry.  
Well noted thank you both. I am looking for two but was willing to settle with 1 in a center placement as my rack is not in the center... but this is another reason I'll pass on the ADS, if I want 2 later it will be too difficult to find another in comparable condition.

There are some current subwoofers with onboard equalization that goes well beyond the idea of brand or model matching. Having the ability to equalize the sub to any future speaker choice and the convenience of remote controlled functions might be a consideration.