Well, for what you describe, the dt880 600 ohm sounds exactly what properties you want. Would you be using this mainly for gaming, or a mix of gaming and music? And what is your preferred sound signature? The 58x does have good imaging but can be lacking soundstage wise, and I think the brighter signature of the 880 can help emphasize spatial queues, and the 880 is better at recreating a space and pinpointing sounds in that space. The 58x can do this, but not as well. The 58x is more tuned for music, and while the 880 wasn’t designed with gaming in mind, it’s signature and properties work very well for it
Regarding the amp, I wouldn’t recommend the magni 3, but the magni heresy is pretty good (but their modi dacs aren’t that great). What is your budget for a dac and amp?