I've heard these before, although I didn't own them. The Q701 I thought was crap. The DT 880 seemed just very flat with maybe a tiny treble spike but overall nothing unpleasing to the ears, although I can probably agree that it can sound a bit artificial sometimes. The X2 I liked too, seemed decent for longer listening too so the bass is not overdone, and I don't really recall aggressive treble but you might be right about that. About your 598SE, did you check if the cable is connected properly, both to the headphone and the source? When I put mine (regular 598) on I had a weird sound with more sound in the left earcup and mainly graininess in the right earcup, so i checked the cable and apparently it wasn't properly insterted into the earcup during packing, because when i reconnected it the sound was balanced again.