This is a pretty good deal on some awesome headphones with terrific imaging, although a bit lacking on bass. However, the AD900x is selling on Amazon for $104, a headphone that retails at MSRP for $300. That's the best deal in this line, at about 65% off. If on a budget, get the AD500x at $60. That's a great deal if treble is more preferable than bass. At about $70, the competition is the Philips SHP9500, with removable cable that can BoomPro, bass, and great comfort. The "wings" of the AD series headband is a bit overlooked in design. If seeking Audio-Technica sound in open backs with great treble, then go all out with the highest available model, they deliver. My two cents.
gyroscopicsGreat price on both but I can't speak for the Fidelio because I haven't heard them. They look nicer than the SHP 9500 but at $55 you can't go wrong with 9500s.
gyroscopicsDepends on your taste. The SHP9500 is very lightweight and comfortable and can be worn for a long time by most people. Both can BoomPro, the Audio-Technicas cannot. Listening to six string guitar and violin on the Audio-Technicas is pretty sweet.
Josh has some insights. Although he gives too much kudos to Sennheiser for top end resolution due to having beaver ears. Sennheiser can't compare to Audio-Technica when it comes to top end resolution. That's one of Audio-Technica's strength and it has very little competition in that arena, you'd have to go for a pair of Focals or something to beat them in that. But I recommend watching both his videos.
https://www.youtube.com/watch?v=69w06QDA9Dw https://www.youtube.com/watch?v=ZcHxxCtxerg&t=521s
JJDeviloperI have AD900x and I've worn it for 5 hours straight no problem. The most comfortable headphones I've ever tried, no competition here. Other headphones always put pressure either on the top of my head or on my ears (on ear models). This one - neither.
https://www.youtube.com/watch?v=ZcHxxCtxerg&t=521s