So once you have the founders edition dialed in the way you like , if you were to then A/B it against the Fireball 100 I'm guessing you would still prefer the Fireball. In my experience of owning pretty much all the ENGL amps I found the Fireball 100 to prob be the best sounding.
But Im gonna throw in a wild card here, quick story : I had two different Special Editions. The first one I got sound incredible, that actually might have been the best ENGL tone Ive heard. It was a massive tone that was super tight yet thick, brutally pissed off voicing. I didnt have it long though, someone offered me a straight trade for a VH4. I did the trade only because the VH4 was worth more and I had never tried one. So off went one of the best sounding amps Ive had. Fast forward I get the VH4 and it was ok but something was off about it. I end up selling it and I get another SE. Long story short the SE shows up and it sounds close but not the same as the other one, I change the tubes in it, turn it back on and it goes up in smoke. $600 in repairs later I get it back and its still mediocre. Off it goes.
Whats the point in this. No two amps are exactly the same. Sometimes you get one that just has the it factor. I think when you find something like that you should hold on to it. Unless you are positive you dont need that sound around any more. Ya might not be able to get it back. Ive had that happen a couple times with certain amps, I would sell and think no big deal I could grab another one later on.