Although I get euphoric listening to the P-1, I think you mean euphonic, as in something exhibiting euphony. I too agree that the P-1 is more pleasing to the ear by being less dry and neutral, but the P-1 is still fast, detailed, and very natural sounding. It is not warm or mushy, and when sourced by my EMM Labs gear it delivered a spectacular sound.
I have spent less time with the GSX but it is closer to my Beta22 on the same characteristics. If you are looking for pretty purely neutral but not boring then either of those will get you closer it. I do happen to have a very nice Beta22 for sale, if you are at all interested.