Depends on what you mean by "satisfying". A six string guitar in standard tuning reaches down to about 80Hz on the low frequencies (7 and 8-string guitars can reach down to about 40-60Hz) and up to about 1,200-1,300Hz on the high end of their
fundamental note range.
Colorations between say 200Hz and 1kHz are pretty detectable for most people, so starting with a frequency response that is mostly flat under 1kHz is ideal. Once you get down to 200Hz or so, dead flat or elevated midbass for extra body is a matter of subjective preference. Typically an elevated midbass and lower midrange is going to give guitars a bit more body and fullness, which many people like.
Just above the guitar's fundamental frequency range (around 2kHz-4kHz), you will find a lot of
harmonic overtones. These are going to give the guitar its front edge and bite. Too much recession in this area can dull notes out a bit making the headphone sound more relaxed. A little extra energy here, or some selective bumps in the FR can make guitars sound more aggressive. However, it should be noted that this is an especially sensitive area of your hearing and starts to get into a range that can be problematic with cup resonance. If you look at a lot of frequency response graphs, you will typically see headphones roll off a bit before this (maybe around 1,500Hz or so) and then add a tiny little bump between 3-4kHz to give their overtones a little sparkle. You can see it right here on the HE-6 FR:
I hope that kind of answered your question.
I like the Focal Clear a lot, BTW, it's really a fun, well-balanced headphone. Great tuning. Nice bass punch, good mids, not hot up top.... it doesn't give you much not to like.
The opposite of the Z1R... Hmmm.... Have you considered electrostatics? I feel like a STAX SR-Lambda is probably the opposite of a Z1R. I have an original SR-Lambda and an SRM-1 MKII and it's just shocking how well it holds up. The resolution is insane and the whole setup probably cost me $500-$600 max. One thing I like about the original Lambda (and lower-end models like the 207) is the diaphragm is a little bit thicker, so they have a little more tactility to them, even if they are just a little behind the top end models in terms of overall resolution. They are still insanely fast, with microdynamics that only the very best dynamics and planars can dream of touching. Pair them with an extremely resolving source and good power they will reward you.