I've got the HD 599's and a GSX 1000 and it's great for games. I've ran to flags with team mates in BF1 and can hear the difference when they run on grass, gravel, etc. But music sounds terrible through it so use a Fiio E17 with the HD 599's.
As said above, we can tell you what we've used, what we like but at the end of the day sound is subjective and subject to personal taste.
Music sounds good personally with the GSX 1000.
I just don't know if I should return the GSX 1000 and the HD 599s and just get the 373D heeadset. I just need someone to help me determine whether which setup would be more "quality". I'm done with stereo, I hate it so I won't be using it. Sticking with 7.1.
Thanks for replies.