So, here are my first impressions after one day. The sound of the amp is exactly as I remembered it - extremely clear and tidy, with a very punchy bass. Much leaner in the low mids and also a little drier than other ENGL models, with a slightly British edge in the upper mids. In combination with the usual Tube Screamer, there is no better amp for Thrash in my opinion.
When I switched it on for the first time, I was unpleasantly surprised to hear a clearly audible transformer hum, which I had never heard from ENGL amps before. Quite annoying because I sit right next to the amp in my home studio. I was worried that it would annoy me so much that I would have to send it back. Today I opened it up, tightened the screws on the output transformer a little, then measured the idle current - and lo and behold - it was set far too high at the factory, at more than 80%. I then set the bias to the usual 70% and after reassembling the amp I noticed that the humming of the transformer had been reduced to a barely audible level. Phew!