NewKID

I really like my Audio Technica M50. The M50x is out and the main difference is the removable cable. Otherwise, it's pretty much the same headphones. I used to take it with me to trips and flights. Isolation is great once the music is on. The one tip I would highly suggest is to replace the ear pads. There are many available, but a popular one is Brainwavz HM5, The velour pads feel really comfortable.

The HD 598 feel really light, and I can wear them all day if I wanted to. The sound signature isn't my cup of tea, but the sound stage and position is incredible. Super wide and airy (is that even a term?). The high and mid are decent. Sometimes, I find the treble to be fatiguing. The bass is lacking. Some would say it's adequate, but I like my bass. Sound quality is great.

Consider the Logitech Z623, as well. Logitech has a bluetooth adapter sold separately. Chromecast Audio is another wireless alternative.

Klipsch Promedia 2.1 have my vote. Great bass. I found that the mids were a bit lacking, but

I found this this combo the other day. I haven't tried the Fiio A3 amp, but it has bass boost if you wan't it. I like a lot of bass. IMO, the M50 and E10K (and E11) with bass boost on sounds really good. You'll have a taste of the bass head kind of bass.

I use the M50, and they built the same as the M50x from my understanding. The sound stage is really tight. You wont get much distance. I wouldn't recommend getting these cans solely for its sound stage, but everything else is great. Noise isolation, sound and build quality, etc.

Sorry for the late reply. Mid is more pronounced on the K701. The mid-bass has more impact. You're last statement is consistent with what I read comparing the two cans, too.

Are you still looking for in-ear suggestions?

The AKG K7XX are not easily powered with only a motherboard. I highly recommend get at least an amp.

Buy these comfortable earpads

This is the brand I was talking about. They aren't specific to Bose. http://www.complyfoam.com/

I take a lot of flights for work. At the moment, I'm using in-ears for portability and sound isolation. Once, you turn on your movie or music, you won't be any sound leaking in. You can find better fitting foam tips for a better seal to get better isolation. I haven't found the need to use active noise cancelling gear because what I have does the job already.

I have the HD 598 and Massdrop Q701. The Q701 and K7XX are nearly identical. I think the only difference is that the K7XX are a little more warmer sounding. I use both for playing CSGO. If I'll be playing more consecutive CSGO games then I'll choose the HD598 because they are much lighter and more comfortable. They'll magically disappear from the top of your head. Also, the sound stage and positioning are unmatched. The sound quality is very very nice. It has its usual Sennheiser sound signature which is weaker bass for a lack of words. IMO, the treble can make it fatiguing at higher volumes, but that's just me. Not everyone will have the same experience. I didn't that an amp was necessary for these headphones as they are quite sensitive. One other small issue was the headband cushion had cracked. I haven't confirmed what the material is. Some say its sheep skin and some say its faux leather. I really enjoy the Q701. The bass impact and extension is quite impressive for an open back over ear headphone for its price. It's not nearly basshead level, but I think the majority of the users will enjoy it. I think these headphones are more diverse. I'd rather use the Q701 than the HD 598 for other media such as movies, internet videos, and music. The bump on the headband is known to give some users issues, but I have no problem with it. They do have a tighter fit than the HD 598, though. I highly recommend using an amp or amp/dac with the K7XX though. I'm using a Fiio E10K and it power the Q701 just fine. The similarities are common for open back headphones for the price: sound leak, detachable cables, long cables, etc. IMO, you should choose the K7XX as you had mentioned you are sensitive to treble. The treble is more tame and the bass is more pronounced compared to the HD 598.

Any one else have any suggestions?

Take a look at these cans. I think he'll appreciate the larger earpads. If he feels like wants to change the earpads, you can get aftermarket earpads from Brainwavz. I highly suggest the velour for comfort. These will most likely fit other over hear headphones if you choose otherwise.