Sabrina X Anyone Add Subwoofer(s)

First, all of my listening has been done at the dealer with the same amplifier that I use in my listening room.  My Wilson's are about one month out.  Since this speaker is an entry level product for Wilson, I was interested to see what happened to the impact and clarity of this speaker with a subwoofer.  My dealer sells the JL Audio Fathom 12" v2 and for another $5000 and tax I can upgrade, but I'm wondering why I've not read about using a subwoofer with the Sabrina X.  

IMO and based on my experience with the original Sabrina, I would wait, get them in and give them few hundreds hours of break in time. If possible have your dealer set the speakers up for you if they’re trained to do so by Wilson Audio. If your room isn’t acoustically optimized you might want to consider getting that done. Subwoofer would be the last thing to worry about. These speakers have pretty good bass on their own plus properly integrating a sub is usually a PIA. 

Wilson uses their subs with the Alexandrias, so what does that tell you?  My advice, get two smaller subs — you’ll get much better performance.  

Smaller subs .. Do you have specific speakers in mind?

For example REL suggest their S/812 as a mono sub, or S/510 as a dual.  The smaller T9x doesn't have the low end extension needed.  My dealer carries the 12" Fathom v2, but at $5k it would be a single sub in my system.

If going with REL, these are the recommendations for Wilson Sabrina on their Web page calculator.

Small room :  S/510

Medium room : S/812