I have had both JC1+ & x260.8 monos in my house for the past 3 months.
Speakers: Focal Maestro Utopia III with twin REL subs
DAC: Holo May
Preamps: VAC Renaissance Mk V and the Audio Research REF6
I did a lot of back and forth between the JC1+ and the X260.8. In the end, I ended up selling the X260.8.
I feel that, perhaps, for easy to drive speakers (minimum impedance >= 4 ohms), the X260.8 might be better. Their midrange is magical-like in my room.
For my system setup, the JC1+ were clearly better. Most of my listening is jazz & classical & I don’t listen to music very loud (around 75 dB SPL at the listening position). If you have hard to drive speakers and are on a budget, the JC1+ are fantastic.
And yes, the JC1+ are not bright at all - if anything, the complaints generally are that they are a bit dark.