I think, for what you want, do not look further. M-100 seems to meet your needs.
I also have the HD-600s with the iFi Micro iCan, and they do sound awesome. Exceptional space and fidelity.
Although I did miss some bass with my electronic music genres.
So I also started to look for a closed can, that I can take with me on the go occasionally.
After a long research I decided to buy the M-100, and I did not regret it. Great, enjoyable, bassy sound. But very clear overall. Momentums might have more detail, but lacks in bass compared to the M-100 (more neutral, natural headphones), and PM3 is just too expensive. ATH-M50 is a very popular alternative, but reviews prefer the M-100 over them. NAD-HP50 was also on my list, I let them go for different reasons. The winning factor in my case was the price. I bought my M-100 for £142 brand new. While the PM3 for example is £349.
And I doubt, they are more than 2 times better.
M-100 is just much fun with any kind of music that has some electronic element in it. Do not expect high fidelity acoustic instrument sound reproduction, but with contemporary music it is simply addictive, a lot of fun. You won't take it off from your head.