Sitting with the SHP9500s now. Interesting situation. They actually have a very similar sound signature to the GSP600s in terms of where the emphasis lies. They obviously have a wider soundstage and more "airy" being an open set. Bass is actually much better than I expected. Neither headphone is meant for a deep rumble but thought the GSP would be miles ahead here. Bit more "sizzle" to the high end and recessed a fraction here compared to GSP600 (which is a good thing) but definitely has more sibilance.
In gaming the SHP seems to have a more washed out sound especially when it comes to gunshots. At least with early testing imaging seems about the same in gaming, I can easily tell direction with either headphone but I think perhaps when it comes to separation and judging of distance the SHP does better due to it's open design. I will have to do much more testing though but at this stage the GSP seems like the more immersive option, it really does sound great in games. In terms of overall music sound quality I don't think I could pick a winner yet they're just...different. This was all done on the uDSD so I may have to check things out with the onboard sound for those looking at these as a budget all-rounder.
As for build quality on the SHPs, they seem well enough made but don't hold a candle to the Sennheisers. Comfort wise the SHPs are nice and light with very little clamping force. Add the decent headband and they can definitely be worn indefinitely. The ear pads aren't great though, they aren't very deep so my left ear touches slightly on the driver which is a mild annoyance. The pad material certainly isn't very luxurious either, then again I am coming from the
amazing ear pads that the GSP has. I reckon an earpad upgrade on these would be a nice touch. Overall they definitely sound very good to someone busy putting his toe into the rabbit hole considering their price. I am sure for someone looking at something cheaper for gaming and music these would work well, certainly FAAAAR better for music than something like a Corsair Void that costs about the same. Bit unfair of me using a pair of Sennheiser gaming headsets for a comparison.
Not sure if they will improve/change as they burn in (If that's even a real thing). Anyway I will listen to them for a long stint before drawing further conclusions. Have to say though once the 6XXs arrive these may become a bit redundant and I may just sell them unless they turn out to give me an edge in gaming. But seeing as GSPs have a great built in mic and build I reckon it's going to take a lot to replace them. Fidelio X2 or DT990 comes to mind but for now I am going to worry more about music with the audiophile headphone side of things and just switch to old faithful for gaming.
Have to say I'm extremely excited for the 6XX's , I reckon the "smoother" more laid back tone they're known for is going to suit me well.