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 added a small Velodyne MiniVee to my Spica TC-60s and it created a balance that rounded out the sound nicely.  I pushed it with an Emotiva PreAmp and a couple of Yamaha amps bi-wired to the Spicas.  

Doesnt have ave the thundering boom that my SVS sub has on my theater system. Just good clean bass.  
Hmmm.>I suggest that you look for a 12-inch dual VOICE COIL system.Not seeing a lot of those advertised?Ben
To answer the question I seemed to have missed, after hearing a friend's system years ago utilizing one REL and liking it, I was looking around on Ebay for any reasonably priced REL and found a Q150e that was missing its grill for 200 bucks. Had the grill frame though, and otherwise was (and is ) perfect...stapled a new grill cloth on the thing and used it alone for a couple of years...great sub, 10" front firing, lots of adjustability. Next I found a mint Q108MKII (8" downfiring) also for 200 bucks, and its addition to the mix is great...note that a lot of the tedious yammering regarding proper setup or additional electronic crossovers, room treatment, etc., can be ignored by simply hooking the things up and moving 'em around some until they seem to work. I use mine in mono (hooked up together to the same amp binding posts) as they're simply not directional as bass position cues come from somewhat higher frequencies, and the subs in tandem work together to cure some room issues. Bottom line...use in a room with furniture, hook them up an enjoy them...I made my own cables with Canare Star Quad, but many used RELs come with a REL capable cable.
I have Hegal H160 with Fritz's new Carbon 7 MKII speakers and recently added a modest Definitive technology subzero sub and a Paradigm crossover.. My room is about the same size as yours and the sub does make a subtle difference in filling in the bass at levels below 40 HZ. Here is how I set them up. . Connect the Hegel L and R preamp outputs to the Xover L and R low level inputs. 2. Connect the #1 subwoofer output to the input of the subwoofer. Sub output 2 doesn't support the phase control. 3. Set the subwoofer cutoff control to about 80-100 hz. 4..The phase control allows you to "synchronize" the motion of the sub with the woofer in the main speakers. Put on a recording with a prominent kick drum. Adjust the phase control so that the total amount of bass from the sub and main speaker is maximized. If the sub and speakers are very close it may not make a big difference. 5. Now you go back to the level control and fine tune that with different recordings. 6. Now go back to the cutoff control. If your speakers are small you may want to raise the frequency to 120hz. If they are large you may want to lower it to 40-60hz. It will depend on the room as well. 7. Now you can adjust the phase control again so that you blend the sub and main speakers. Don't worry about getting it perfect at first. As you play the system with more music you can fine tune it. The Hegel has great bass so you will probably notice tighter more dynamic bass than before. The H160 is broken in but will sound better if you leave it on 24/7. Enjoy