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
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,
I had a Janis sub woofer with a pair Thiel's  20+ years ago. Now, I am starting a small system with a Peachtree Nova amp and Definitive Technology SM 45's. The speakers sound nice but I do miss the low end. What about the new ELac wireless sub's?  Anybody test drive any of those? I like the flexibility of moving it around the room without the wires.
Thought I would mention my setup, consisting of Moon 600i integrated, Focal L&R Utopia Be loudspeakers, (45Hz-40kHz) and one JL audio e110 subwoofer. Room is about 15x21 and 7.5 ft ceiling.


The Focal speakers are ported with two ports on each one, I have spent much time experimenting with plugging ports. One plugged, vs two plugged, etc. In the end I decided they sound best with both ports open. Also after lots of experimenting I have found using the low pass crossover set (according to the dial) just under 35Hz provides the most accurate sound. 

The difference between the listed low frequency response of 45Hz by Focal and using <35Hz crossover setting on the e110 seems like would leave a hole in the sound field, but I have found if I set the e110 closer to the 45Hz of the Focals it only exaggerates the bass frequencies in the maybe 40Hz -60, 80+ Hz range? 

I would also suggest look into the Soundoctor setup advice and CD at www.soundoctor.com, can be helpful. It has been a long road but my system is sounding great in all respects! 

Gary