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

Well I can hear the difference in my system after getting my T-Zeros dialed in. 

This is a very old discussion.  I wonder how this got started again.

I added two REL SHO's and it was a game changer.

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.