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, I have SF Venere 2.0 and needed a little more low end for certain types of music. I was pointed to the Sumiko s.5 because it matched the tonal qualities of the SFs. I have been impressed with how the sub is almost undetectable the way it just fills in the lower frequencies without sounding like an extra speaker. Plus it looks damn good. I have it attached via the speak-on cable to the b speaker outs. 
Room is 13.5x12.5 with 9 ft ceiling. 
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I highly recommend you look at SVS brand subs. There aren’t a lot of reviews, they are very positive. I just added an SB1000, their smallest and least expensive model, to my small room, bookshelf speakers system, and I’m thrilled. Good luck!

+1 to danatek’s combo of Martin Logan Dynamo 300 with Magnepans. I have the same sub in a 15x20 room with MMGWs on the 20-foot walls. They have no bass but I wanted a fast sub, so I went with a small  one. Just take the time to really listen to the mix, considering how low your speakers really go and just dialing up the sub volume until you’re more aware of feeling the sub than hearing it. 
I'd give serious consideration to Hsu. I run a pair in my AV system and have occasionally run the audio only system through them (I don't need them for that as my main speakers are 3 dB down at 20 hz), They were well behaved (when properly set up) and fit in well.

That opinion is based on experience with only the VTF-15H Mk 2 units and I make no comment on any of the other models that I have no experience with,