In regards to the output impedance: What you mean is the damping factor.

https://en.wikipedia.org/wiki/Damping_factor

it can make a lot of difference if you have old gear like a receiver with 30 output impedance. (My starter gear)

When people switch between solid state amps and they say “oh it sounds xyz” it’s not the amp, it’s the output impedance and the gain most likely. (Which is the amp but you get what I mean)

My old amp had 5 gain (no gain switch). My new one 0 gain. Sooooo much better like damn. (Which is why I got a new amp. Anyone want a magni 1st gen? I spent like 200 bucks on my new amp tho, no need for ultra fancy gear)

I could never stand the beyerdynamic treble peak, I had dt880 for ages and had to swap. I’m just too sensitive. They are great headphones imaging wise, I’d just wish they’d get rid of that damn brightness.