Adding a Second Sub

I am debating buying a second sub to have stereo subs. I have Sonus Faber Extremas and a Rel Stentor. I would really like to hear from people that have done this and what they thought of it. Were there any drawbacks? What were the advantages? Did it make a huge difference?
Deffinately two subs. I added 2 B&W 800 Matrix subs to my
801 III and will not go back. It was a match problem for
the 801's and the only seemless blend was another Matrix
12" sub. I have them reasonably low, but can really hear
and feel the difference. If it plays well together, go for
the lows.
If you are crossing over low enough, then you don't need two subs for stereo as Faberryman and others have pointed out. But two subs often gives a better result - the main reason being that you can get smoother response. Some subs use two drivers, one on each side, and their separation by a foot or so helps to get a smoother response. It is just that each driver will create room nodes and anti-nodes in different spots and (hopefully) cancel each other out. The downside is that set-up requires even more patience and time than with one sub. From experience you will very likely get a significant improvement with two subs, but two Stentors is a big investment in the bottom octave.
I started my first system with Aerial 7's...added one Vandersteen, what a change! BUT, the most noticeable change was not in the bass range, but how the 7's opened up and became more dynamic. Subsequently, I added another 2W, and BAM, once again a step up in the performance of the 7's...Take out one sub and its like a v-8 running on 6 cylinders...I vote for two subs.
two subs will improve *all* aspects of a two-channel stereo system - better room-integration, better soundstage, less distortion for the same wolume level. go for it! :>)

doug s.

I agree with Sedond and others. You want stereo, not mono.