Dual vs single sub

Stereo bass? Vinyl mixes bass to a single channel for practical reasons. Moreover, localization of low bass is a non issue as you can't really tell where its coming from, only the higher harmonics is a clue, AND most music only have one bass instrument. 
More subs is for other reasons, but stereophony it is not.
Room aucoustics really need to be covered. Buy a measurement mike.
Use REW program, its free.

Your best bet to archive deep clean bass is missing subs together from 2-4 brand 
im using SVS PC13 ultra with two klipsch SW-115 
way better than using only one brand 
also use both red and white outputs with Y adaptor  don’t use only LFE 

https://www.amazon.com/Mediabridge-ULTRA-RCA-Y-Adapter-Feet/dp/B00KCQSW3E/ref=mp_s_a_1_11?crid=2ENEO...

You want two. Most subs have to cover a range from low bass, which is 'locatable' by a listener, to very low bass which isn't  and the power needed to produce a given spl is only 1/4 as much with a pair than it is with one.

Best test is to play a CD of organ music with low notes with no sub, then with one, and finally with two - makes a big difference and moves you, the room walls and anything in between.

You need pretty decent quality subs to integrate well with hi fi audio. The best bang for the buck I could find was the  VTF-15H MK2 DualDrive 
http://www.hsuresearch.com/products/vtf-15hmk2Dual.html
110 lbs each, 600 watt on board amps and they look pretty decent, not like something that got drop kicked off the back of the band's bus.

@vt4c, a timely reminder. Nice, just before someone suggested 8 or 16 subs!

Stereo bass? Vinyl mixes bass to a single channel for practical reasons. Moreover, localization of low bass is a non issue as you can't really tell where its coming from, only the higher harmonics is a clue, AND most music only have one bass instrument.
More subs is for other reasons, but stereophony it is not.

While most of this is true, the comment about vinyl is not. We don't mix bass at all when mastering. That is a technique used to reduce the time and cost of mastering time but its not something cast in concrete.