I had the HD598. If the modded HD58 is the same as the HD598, the that is the BEST way to go (I honestly don't believe that it is, unlike the modded 555 and 595, Sennheiser can't possibly be that stupid to do such a thing again).
The HD598 is the best headphone I have used for gaming that didn't require an extra amp. Better than the AD700, PC360, AX720, Beyers, and what have you. They sounded like a K70x with more bass (though they aren't bassy themselves, and less soundstage, but still large overall.)
So if I was empty handed right NOW and didn't need a mic or didn't mid attaching one, the HD 598 + Mixamp 5.8 would be the way I would go. I don't particularly like the HD598 for music, but I liked them better for music than the K701 or AD700, which are the only two headphones I'd rate slightly higher in purely competitive terms. For around $160, these are pound for pound my favorite gaming headphone.
If you plan on attaching an amp, I would choose the DT990 (600ohm in my case, YMMV with the other versions) over the rest due to it being good with everything, from fun to competitive gaming, movies AND music, IMHO.