Now if you had to choose between the DT990 and Q701 what would it be? I'm really thinking about picking up a DT990 one of these days.
The HD598 is more like the K701 than the Q701. The HD598 is outright boring compared to the Qs. The HD598's mids are more forward and richer, while its bass is a step behind the Qs.
The Q701s treble is never sibilant. They are smooth, but with enough sparkle to satisfy me, and I'm a treblehead.
The bass on the Qs is just better. Drums sound spectacular off them. Its the deep low bass where the Qs don't excelin, but the punchy mid bass is stellar.
I'd say the Q701 sounds of higher quality overall. The HD598 is great for analytical gaming, but nothing outside of its very involving mids will grab at you. The Q701 is more engaging as a whole.
I'd recommend the Qs every time, over the HD598.
I wanna mention that I'm very sensitive to mid bass. Mid bass tends to giveme headaches if its too emphasized. The Q701 has strong midbass, yet the way it hits never gets annoying, which is quite a feat. The impact diffuses in a way that it doesn't feel like a hammer hitting the side of my head. Its quite satisfying. Its not a bass monster, but its surely not lacking in impact. If a song calls for it, the bass will be there.