Welcome to the forum KR500!
Presently I do most of my listening through speakers, but I do have the Audio Technica ATH AD700 headphones (same as your old ones). Truth is that my speakers have better resolution than my ATH AD700 headphones.
One reason I like the AT phones is that they are very comfortable to wear (and don't laugh!) they don't make my ears feel hot. A few years ago I had a set of Sennheiser HD600, but I could not wear them for a long time because they made my ears too hot and uncomfortable, and I felt that they contributed to earwax buildup.
Are the ATH - AD900X headphones as comfortable as the AD700? I read good things about them in Stereophile magazine.
I am thinking of getting a better set of headphones, moderately priced of course, and would appreciate suggestions. Light weight and comfort are important to me, as well as the sound.
I love my AD900x, its great for the price! I pretty good upgrade over the AD700.