I've played the Screamer, Thunder, Fireball 60, Powerball, Savage120 (I own one), Morse, Invader 150
I think the "large chassis " Engls are quite different to the Screamer/Thunder, neither of which I particularly liked. The Fireball 60 is a great sounding amp, I really liked it - & not just a one trick pony either, although there is a shared Eq, the clean channel was quite good. If a two channel amp was all I wanted, it would be near the top of my list.
I liked the Powerball, though if I owned one I'd leave it set to "Classic" mode - I couldn't find a single sound I liked out of "Modern" mode. Even with shared gain controls between ch1/2 & 3/4 I found all 4 channels balanced well with each other & liked the range of sounds. I've heard people say that the Fireball uses the same gain circuit as the Powerball's Ch4 but I'm sceptical - they sounded different to my ears (although I didn't get the chance to play them side by side) - the Fireball seemed a bit more "open" to me.
However, the Engl I chose to buy was the Savage 120 & I have to say it's one of the best purchases I've ever made. I took a trusted friend/colleague at his word & bought it without having tried it. The twin FX loops & 6550 power section were what first caught my interest. IMHO it's superior in every way to the Powerball.
Since then I've tried the Invader - very versatile, lot of sounds available, LOVE the MIDI switching (absolutely fantastic, well thought out system), but I still think the Savage has a better modern metal sound.
& the Morse - some of the nicest clean/crunch sounds I've ever heard but for the life of me I could not get a metal sound out of Ch3 that I liked. Since then, however, I found
this demo - if it had sounded like THAT when I played it I'd have bought it on the spot. Would love to try the settings he's using there into a V30 cab, which brings me on to:
CABS: If you can, try an Engl you are interested in through a few different cabs. The Engl "std" cabs using Celestion Silver Series V12-60 speakers have quite a dark, scooped sound to them which suit the Powerball & Fireball quite well, but sound vile with the Morse. The "vintage" cabs have Celestion Vintage 30s & sound great with the Invader, good with the Fireball, but a bit "harsh" with the Savage. FWIW, I use Classic Lead 80s & G12K100 speakers with my Savage - they are far, far better than V30s for that amp.