Your comment about me being used to super bassy headphones is absolutely true. This was my main concern when I ordered the TH-X00s on Massdrop: am I going to feel a little disappointed by some "relative" lack of sub bass?
I recognize that the perceived quality (definition, clarity, impact) of the bass (and sub bass) on the TH-X00 is a good level above the M-100s, I just wish it had a flatter response below 60Hz (I know I'm being picky)
I had a X1, HE400, TH-600 a few other headphones when I got a M-100 and after about 2 weeks the M-100 was never used again, ended up giving them away to a friend who had Beats Pro. The TH-X00 was to replace my TH-600 but after a week the TH-X00 was the one that was let go, the TH-600 sounds clearer, goes lower and is much more comfortable for me, mainly due to the stock ear pads. I might revisit the TH-X00 in the future if I find pads that work better.