The Tsunami amps are in fact designed by the same people who did the Avionixx equipment. The 1100, 4440, 1800 internally are not as beefy you might call it as their Avionixx counterparts. Avionixx really stresses some types of PCB's and chips to get a little more performance out of their amps (which inherintly makes them more expensive obviously). Coating some parts of the electronics keep up power output longer. (I'm not a electric engineer so all I can really do is forwarding my understanding about it.) That was a nice thing about the avionixx amps, is they are, and they know the answer to all that picky stuff I just can scratch the surface of.
The Tsunami 1800 is essentially the beta version of the 1800.2 from avionixx. Since then it's been tweaked to do a little more power, work in the Avionixx case (tsunami cases are a little larger), beefed up the power supply, and as far as I know stacking them and making the next gen of 1200.2 stackable as well. Problem is we can't build the 'next gen' units until we get the tsunami units outa here.
If you want to look at them in kind of a interesting light as if they were one line where would it fit. Think of it as when you see the Arc line the KAR is great stuff, and the XXK is the little bit beafier, sturdier, more detailed stuff. Think of the tsunami stuff as something like a comparison the KAR, as the avionixx to like a XXK. Doesn't mean the KAR isn't good, or that the tsunami amps aren't good. It means there's a step further it can be taken like in the XXK or Avionixx line. -Hopes that made sense to read- lol.
Ben