My new amps

I recently bought two USED Arc Audio 2100cxl's.  I've heard a few good things about them so cool.  I hooked them up last weekend to make sure they work and had some gain questions about them. https://www.the12volt.com/installbay/forum_posts.asp?tid=36236&KW=gain

Still have some questions, but the amps rock.  I drove 225 miles to install everything and do some custom woodwork with my pops and grandfather.  On the way over, my pcx-440 got REALLY hot after two hours.  On the way back the Arc's were warm and thats it.  The gain thing still vexes me.  The formula tells me that it should clip at the voltage its running at pretty early in the volume.  The gains are pretty much all the way down.  Which brings me to the next thing that surprised me.  I was thinking that going from 25w rms to 110w rms would be a large difference in volume but it wasn't that big.  I thought maybe it was because of the "gain thing".  I had set the gains at 75 percent of max volume from my HU, so I thought I'll just turn it up until it distorts.  It never did.  I turned it all the way up and it was pounding but it was CLEAR.  I thought there was some distortion but it was all the plastic in my truck rattling.  (didn't know I had that problem). I was impressed to say the least.   I'm sold on Arc Audio.  Just thought I'd share.