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 wanted to post a shot of my IDEA Sub connected directly from my PassLabs XA25 amp in parallel with my PMC Twenty26 using Western Electric speaker shielded cables by TimePortal. Anyway the package of one sub and PMC sound wonderful. I couldn’t believe the results. The PMC stopped chuffing and the bass balanced beautifully. Using the sub crossover and level allows to customize to meet track needs. I’ve never looked back. Thought of trying other subs. This one is a 10” active and passive dual design. Works a treat. My bottom line? Experiment.
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 It has been superceded by the Dynamo 400 , an excellent product and an excellent value.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.