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
Many recommend 2 or more subs, I know REL does. Some depends on how low main speakers go and room. Also debate about how directional our hearing is below 35-40hz. Bass guitar goes down to 42hz. So lots of debate, and different preferences. REL likes to demonstrate subs with female vocal and acoustic guitar...
Naive question: doesn't a sub mess with the image?

Say you've got a bass guitar mic'd mostly in the left channel but then part of that instruments frequency response plays over the sub which is in the middle of the two speakers. How can that possibly sound coherent image wise? 
casteeb, if you’re asking me, I’ve had a few speakers in there, most recently Canton Vento Reference DC9 speakers, which have a surprising amount of bass for small monitors and before that, Klipsch Heresy, which despite having a 12 inch woofer in a sealed box, don’t dig very low. The sub complements both sets of speakers nicely. I also use subwoofers in my main system with legacy audio focus 20/20 speakers which have a total of 6 twelve inch drivers.
I added an Omega DeepHemp 8 to augment my Super 3i Monitors. I was really unsure if this 8" driver (down-firing, sealed design) could be satisfying. It made a world of difference. Yes, I'm thrilled. I doubt you'd be disappointed with any of the ones you're looking at. 
A number of the Rythmik plate amps (all but the XLR models) provide both high-level connections (on speaker binding posts) AND line-level connections (on RCA jacks). You can try the sub both ways, and use the method you prefer.
It's remarkable what a sub can do for mids and highs...I use a REL S/5 SHO, but have had great success in past with small REL in small room system...
All of my systems include a subwoofer (or two or three or...).

I have a couple off small computer systems in smaller rooms and use small sealed subs in both, a Rythmik F12 in one and a SVS SB12-NSD in the other. I love Rythmik subs and think they are hard to beat for the money, but SVS is no slouch either. The SB12-NSD is an incredible bargain right now. They have been discontinued and heavily discounted. You should add that to your list. 
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H160 has variable Line Level (RCA) right, left and the node2i I'm adding will also have sub out.

I'd like to get both R+L into the subwoofer.

Some controversy with adding REL high level off the speaker outputs. Hegel says no don't do it and REL says they have done it at shows with Hegel.... thus the can of worms of subwoofers.




Yes a sub warms up the sound...

I love my 2.1 setup with Velodyn sub. 

You won't be disappointed with a good setup.

Does your pre have a sub out?