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
Ive had a set of Magnaplanars in a room of similar size to yours, and have always found large, slow 'subwoofers'i.e. Velodyne, JBL, etc just result in muddy, discontinuous sound. Not expecting very much, I tried a Martin-Logan Dynamo 300 8" powered sub and found it filled in the bottom end seamlessly. It has been superceded by the Dynamo 400 , an excellent product and an excellent value.

I couldn’t live without Subs.

I spent years box swapping.  Never satisfied.   Now I realise I’ve had a lot of very decent kit that would probably still be here if I added the missing ingredient earlier.

The JL Audio e-sub 112 has internal Hi/Lo Pass Filter.   I feed the sub from my preamp, then out to the power amp for my mains (P3ESR).   
Crossover set to 95Hz
This takes a load off the mains & liberates them.
Also removes any bass lump.   It’s seamless.  Doesn’t sound like there’s a sub.  

I definitely recommend giving this method a try.
The OP has an integrated amp. You can only do that with a separate amp and preamp. He will have to run his speakers full range. I use the JL d110 (no high pass filter) with the p3 and it blends nice!
I went through  subs. Big ones, small ones, from Hsu, Infinity, DIY, Horn, Isobaric, compund, etc. .Found they all degraded the sound. I tried a cheap servo-sub, and loved it.
Its the only type sub I can live with.
I use a pair of $150 buck Yamaha servo-subs, with my small Proac monitors. Marchand passive 4th order xovers.
I may upgrade someday to some more expensive servo subs, but for the last several years, they have satisfied me quite well.
I added an 8 inch powered sub to my ADS 300s and it is wonderful
The ADS are good down to 100hz and the sub adds exactly what's missing. The 300s Mids and Highs are Hard to beat at any price range.