Pairing a sub with A/D/S L1290s

http://sportsbil.com/ads/pb-1500_om.pdf

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.   

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.  

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.