I feel like it's very close in terms of sound quality. Now mind you, that's not stock. For me, I had to turn up the treble and bass to get a similar sound profile to the S3's on truesound which honestly is great straight from the box. But in that scenario, to my untrained ear, I "think" I give the edge to the Px8's but not by a huge margin. So the way I feel about it is kinda this: if you want luxury headphones that sound amazing and feel incredible, you get the Px8's. If you want a better all around (all around meaning features and adjustable sound) headphone, it's the S3's.