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
Yes, I have done just that.  But I had Magnapan speakers at the time.  It was wonderful.  The music exploded!. I currently have full range speakers now, no need for a sub.  That said if you beside to get a sub, check out "REL".
A sound system that wants great power efficiency will definitely require you to use a subwoofer. Subwoofer has many good types, such as: JBL 728S, Martin S218, EKX118, BMB, Bose ....
Refer to the subwoofer product at http://bit.ly/2SjOdMZ
No brainer - haven’t read the other posts just be careful.  Definitely go with two subs if possible and place each one as close to each bookshelf speaker as possible to minimize any timing issues.  Just go small - 8 inch driver.  Rythmik are great so are REL T Zero’s.

I have Raidho XT-1’s and I’ve paired them with B&W PV1D’s and I would put this system up against the best full range floorstanders on the market.

I can also use this to watch movies with outstanding results due to the improved bottom end.  I cross mine over rather high at 80hz at the advise of Raidho.  Call your speaker manufacturer to get tips.

Rob
I currently have a set of KEF LS50’s in a large room, 20’ x 24’ x 9’. They are on stands and I’ve used two different configurations. The first was a set of one cubic foot Klipsch 8” driver with two passives. The second sub sat directly on top of the first. I tuned them together andnthe sound was as a single sub. One coming in lower and the other tuned just a bit higher.
Great sound but I needed to thin my gear. Sold them quick and easy, still miss them. One cubic foot with 350 watts each was a very nice sub. They were 308’s

The second setupmwith the KEFs was with a 10” sun from Klipsch again. 
Side Note; I love the PSA subs I have for my main system but they are huge and multitask for HT.

the 10” sub does a very good job as well and is set up and being used as I type.
Have fun!
I added two REL t9/i subs to my 2-channel.  Being somewhat of a dumb 2-channel purist and wanting to keep everything planar I was resistant to add the subs. 

Ive finally come to accept that I now have separate subs in the room and the sound is fantastic.  Just the right amount of room pressurization allowing for excellent slam in upper base and extension in lower frequencies.

I can try just powering a single sub to see how it compares and get back to you