One SVS PB13 Ultra or two SB13 Ultras?

I presently own a SVS PB13 Ultra in piano black in a 14x20x8 home theater room. Carpeted floor, right side half-wall opened bar, back wall centered French door opening. I need to know if anyone has done a comparison with a close-to similar setup with 2 SB13 Ultras and with 1 PB13Ultra. My preference is 60/40 movies/music. My speakers are Casta Acoustic model A's across the front with Axiom QS8's as surround duty - all are extremely efficient. I do have the SVS AS-EQ1 sub calibration but haven't incorporated it yet into system. Please include any details as to sub placements, quality of bass, to response. My idea of quality bass is chest tight, detailed, accurate , fast & controlled with great low level extension. I do like music/ movies very loud....

Thanks in advance.
I replaced one Paradigm Servo 15 with two SB13 Ultras. It was better, but then I took Jim Smith's, of "Get Better Sound", advice and now run them in stereo, even though they are crossed over at 40 Hz. More even response, better image, not too large a set up, even with two. My room is similar in size to yours, but I am just set up in stereo, with Maggie 1.7s. SVS advised me that one woofer would be enough, and that they would be fine in mono, but I like the result better with two in stereo. I use two DSPeaker antimodes, one for each woofer. You know you could return one, if you felt it was a bad fit. I suspect it will be the same as with TV screen size, get the most you can afford!

For overall balance in the room, I would encourage twin SB13 Ultras over one PB13 Ultra. Of course one PB Ultra will go deeper(16Hz) with plenty of authority, but two SB Ultras, if set up properly, will sound better with music and still provide plenty of ooomph in the sub 20Hz region. I added an SVS SB13 Plus(95% same as Ultra) to my existing Revel B15 and Klipsch RSW-10d, and my system is finally where I want it to be with HT and music.

I would suggest you run your SVS AS-EQ1 calibration before you lay out any more $$$, and see where it takes your system. I owned my NAD T175HD pre/pro more than nine months before I ever used it's Audyssey MultEQ XT calibration. Only after I bought the SVS SB13 Plus did I do so. What a huge improvement over manual setup.