Can anyone hear the difference when you add REL subwoofers when playing two channel

It took me over a year before I was finally able to get my pair of REL T7i integrated properly. 

The first time a heard REL subwoofers was with one T9.  The key is to add two large size REL's.  Otherwise, they really don't add much.

I am going to expound a bit on my original statement of a year's time to integrate. I had never had subwoofers in any iteration. Not in a vehicle even. I had followed RELs instructions in the manual for setting these up. Using the hi level speakon I had limited but unsatisfying results. No matter where I put them or how I angled them. I fiddled with crossover and gain setting knobs more than my wife's knobs. I gave up after a while and at the advice of another forum member and hooked them up via RCA and used my integrated's subwoofer controls and low/ hi pass filters. This gave me what I was looking for or so I thought. After using them in this manner I started thinking, "Could it be better?" and "Why does REL insist the Speakon hi-level connection is best?" These thoughts propelled me to seek. I went back to hi level and worked at it some more. Still disappointed. I reached out to REL and after quite a length (months) of time I was finally contacted by a tech. He had me turn my gain about halfway up and my crossover at 0. I had to 'walk' the crossover up slowly to hear it finally kick in. In other words, I had to not hear it before I could finally hear it. From there it was a matter of listening over a few days and adjusting which, in my case tended to be adjusting down incrementally on both crossover and gain. Have I got it perfected yet? Don't know, but I am finally getting what I paid for and it makes a huge difference in every aspect. Satisfying lows, thump when needed, grab you by the keester, rumbly in your tumbly bass if called for, Timbre, clarity of mids and highs and a much improved soundstage.

My journey could have been shortened quite a bit if the advice of bringing the crossover up from zero slowly had been in the manual. It is in a video online buried in the archives but I never knew about it. It also could have been shortened if REL had been more responsive to my emails and texts. I had almost given up on them but now they are tuned and integrated they are very good. Are there better? More than likely. But wow, what a difference.

a single REL S5/SHO immediately made a nice improvement to my large tower speakers...I added another a year later, and also an immediate benefit...I used a T/9i with Magnepans in a smaller room and also, immediate quite noticeable improvement...have also used the REL T/Zero lll with small monitors and they add a nice bit of lower frequencies, though not typical "subwoofer" but quite enjoyable...

dadork, clearly, your not a dork.

The improvements I think your seeking can be accomplished with the sub and room relationship, third party monitoring and equalization products using your subwoofer low level inputs. Unfortunately your subwoofers low frequency response has its limits in comparison to many other brands. 

Regardless, there aren't many low frequency rules. Your satisfaction is everything. Good luck with it.