Has anyone added a small subwoofer to 2 channel and been thrilled with the result?

You won't be disappointed with a REL.   My T/7i made an instant difference in my 2-ch system.

Thanks for the explanation guys, and sorry to hijack the thread.

Very happy with my REL S/3 SHO. I’ve got it tuned for just enough to fill in the lower end with some oomph and not get kicked out of my apartment. Wired up using the high level input off a class a/b amp, which it looks like the Hegel H160 is too.

I’ve had excellent luck using an old 8” 100watt Energy Sub in conjunction with a pair of Triangle Titus small bookshelf speakers driven by a 10wpc Cayin EL84 tube amp. I use the speaker level crossover in the Woofer at a 60hz crossover. This is my bedroom system and it gets used virtually every day with program sources ranging  from vinyl, CD and FM to internet radio.

Here's my transition the past few months from two speakers to a 2.1 system to a 2.2 system.

Started with a humble stereo...  Yamaha CR-2040 receiver and a pair of Advent Maestro speakers.  Clean, clear power to those donut midrange speakers- this is *great* low-buck audio! ... but you're clearly not getting the lowest of the low end.  And that's how it's going to be with many passive full-range speakers....

I don't want to shake the place- but I want the low end of the strings, percussion and brass represented completely.

Started by adding a single REL S/3.  $1000 for the sub was lots more than I had in the entire rest of the stereo.   Used the cable that taps the L and R speaker outputs.  Very significant improvement!  

Considered adding a second REL S/3...  My room is about 25 x 20, on a bass-sucking crawl space.  I could tell simply adding another S/3 would be much better... but I decided to simply cut to the chase!

Worked out a wonderful deal on a pair of REL 212/SE and I'm here to tell you.. even without using Unicorn-quality components my (formerly inexpensive) stereo sounds world class.  Not set up to boom and rattle- but the substance and dynamic power the REL's bring to the audio is unbelievable.  

Not sure having subs "in stereo" matter all that much... but having the low end filled out by one or two subs is the best tone upgrade I could have possibly made.  In essence- I took a junior varsity stereo and brought it into the major leagues with some high-quality supplemental low-end.  Best audio money I ever spent.

If the subs were boomy A-V... then absolutely not.  REL have been very musical for me and I would spend that money again in an instant for the improvements I received.