Oh man I went through the exact same thing for the exact same reason earlier this year. Boredom and working at home led to me buying and selling/returning WAY too many headphones.
From memory, short reviews:
Sennheiser HD6xx - this is my favorite and the one I kept. I like it especially for guitar. Think of the 598 with additional fidelity and clarity and even frequency response. It's not too bright or too dark which is good for distorted guitar. Music is good too but it lacks low end punch and high end sparkle.
Sennheiser HD58x - similar to the 6xx but with more low end and less treble detail. I preferred the 6xx so kept those.
Beyer DT880 - my second favorite, although it is much brighter than Sennheisers. That ends up being fatiguing and overbearing, which is why I didn't keep them. Better build quality and more comfortable though.
Beyer DT770 - similar to the 880's but with a stronger and flatter bass response, a little more sucked out midrange, closed so they were good at sealing outside noise. Preferred the 880's.
Audio Technica M50x (and M40x) - really weird response to my ears. Way too much bass and sucked out midrange with a funky upper mids. Everything sounded out of sorts and unnatural to me. Returned quickly. 40's were the same story as the 50's.
Blue Mo-Fi - tried based on the recommendation here. Found them to be kind of small sounding and extremely heavy and uncomfortable. Didn't last long.
Meze 99 Noir - pretty good closed back headphones, comfortable and seals outside noise well. But pretty bassy and not natural so didn't like it much for guitar. Good for music.
Philips Fidelio X2 - there's kind of a nasty upper mid spike that made these things annoying to listen to.
I also got into bluetooth wireless headphones. I tried Bose (QC35, 700), Sony (XM4, XM3), Beats, maybe others I'm forgetting. I ended up keeping the Bose QC35 as they were a little smoother sounding and comfortable, even if the 700's were better for calls and Sony's had more bells and whistles.
