Agreed - I'm honestly not really a fan of perfectly flat-as-a-board sound signature (at least not the music I listen to). Like you said, it always come across as boring and no energy. It's great for audio mixing/engineering though, but not the sound I want when I'm kicked back having fun.
I assume you looked around on Vidal's site? He has an extensive review of most KZs, and does a very straightforward job of listing the different bands.
Also, it sounds like you have a very specific tuning in mind. Have you ever tried EQ to get it dialed in just right? I have lots of headphones that are close to what I want but not perfect, and a quick touch of 1db here or there makes them perfect. With EQ you can control very specific frequencies with extremely granular control. Much more granular control than headphone manufacturers can generally achieve with basic driver and enclosure tuning. I mean, you can do this or that with a vent hole, foam, tuning cotton, shell volume, pad material, etc. But usually a tweak to one frequency caused a change to another. It's basically impossible to boost 5kHz by 1dB, cut 64Hz by 1.5dB, and cut 12kHz by 0.75dB with physical tuning alone. With EQ it's trivial.
I know a lot of people villianize like it's some sort of evil, but that is just crazy talk when you're talking about something that allows you to take a headphone/IEM that you love every aspect of - except for ONE minor thing - and with the click of a few buttons MAKE it literally perfect. I think if more people used EQ, they would stop the endless search for that "perfect" headphone that only exists in unicorn-land. Our ears are all slightly different - EQ is the great "equalizer" (literally).