Has anyone added a small subwoofer to 2 channel and been thrilled with the result?


The subwoofer can of worms.
I’d like to add some bass to my otherwise fine 2 speaker setup and have limited space so perhaps a single 10in?
After a few weeks of research the only conclusion I can come up with is - everyone agrees they have to be setup properly. Every brand and technology has their own following and most recommend using 2 (which I don’t want due to space concerns). My room is 12 x 13 ft with box raised ceiling.
After much research, these are the subwoofers I’m trying to pick from, for various reasons:
Rythmik FM8  - lots of hifi fans
JL audio e110 - fantastic support
REL T/9i - sort of a gold standard
KEF R400b - interesting technology, makes me grin. 

I've never heard any of these.
System:
Hegel H160
SF Concerto speakers on stands.
Ben
casteeb
casteeb, if you’re asking me, I’ve had a few speakers in there, most recently Canton Vento Reference DC9 speakers, which have a surprising amount of bass for small monitors and before that, Klipsch Heresy, which despite having a 12 inch woofer in a sealed box, don’t dig very low. The sub complements both sets of speakers nicely. I also use subwoofers in my main system with legacy audio focus 20/20 speakers which have a total of 6 twelve inch drivers.
Naive question: doesn't a sub mess with the image?

Say you've got a bass guitar mic'd mostly in the left channel but then part of that instruments frequency response plays over the sub which is in the middle of the two speakers. How can that possibly sound coherent image wise? 
Many recommend 2 or more subs, I know REL does. Some depends on how low main speakers go and room. Also debate about how directional our hearing is below 35-40hz. Bass guitar goes down to 42hz. So lots of debate, and different preferences. REL likes to demonstrate subs with female vocal and acoustic guitar...