I love my HD 58X cans, but they're not great for everything. When I plan on working for a long time on something that I need the utmost in quality for in a quiet room, these just can't be beat. If I'm looking for something that I can take to gigs or on set, then I'd prefer my HD 280 Pro's. Horses for courses.
In terms of sound quality, they're great. Good sound reproduction, good tone response. Obviously, they're not going to compete with an Orpheus system, but I think they fight above their weight class. They pass the my standard "Hotel California" test, and that's good enough for me.
(The "Hotel California" test, at least for me, is listening to the song by the Eagles at a low listening level, then a higher listening level, to ensure that power output is as smooth as possible across different voltages. One must use an adequate DAC and amp for the cans, and I use a Schiit stack. There shouldn't be an abundance of treble at low listening levels and an abundance of bass at high listening levels. The sound should be smooth, but have some bite, without being mushy or crunchy. Hotel California has a wide range of sound, and yields an excellent sound on headphones that can accurately represent the soundstage of the song. )
In terms of build quality, they're fine. They're not exquisite, like some Grados or whatnot, but they're also not going to fall apart after you accidentally walk away with them on and they crash to the floor, true story. That's also a testament to their comfort. I find cans with more clamping pressure great for in the studio or in a listening room. They feel secure, not like they're going to fall off when I move around a little bit.
I paired this with a Schiit stack (Magni 3 and Modi 2), which have more than enough capacity to deliver a pleasurable listening experience. I definitely don't recommend running these off of any onboard audio solution.
If I had to gripe about something, it would be the cord, and specifically the jack on the end. I much prefer the standard HD 280 style, which has a screw lock for the 3.5mm-1/8in adapter. You insert the jack, screw it in, and it appears and feels much more streamlined. With the HD 58X's, it feels like the 3.5mm-1/8in adapter was more of an afterthought. ("Wait, people might actually want to use these with a reasonable audio solution that only has 1/8in connectors! What should we do? Let's just throw an adapter in the box," as opposed to, "well, people are probably going to use this with high end audio equipment, so we'll include our professional connector with the screw lock for the adapter instead.").