Just received my Stax 323S and connected it to my Stax 507. I've had it for a couple of days now, and I think there might have been a breaking in period. Anyway, I have no complaints. I also received the Sieveking Sound Omega Headphone Stand in macassar, and it's a beauty. This is my first experience with stats. I also have an unmodified Fostex T50RP that I plugged into the back of my IMac and really liked it, so I was used to the Ortho sound. I listen to all kinds of music, and the stats handle it all in stride. I don't have a DAC, but so far I'm very satisfied with my setup from the IMac. If I do get a DAC, I'll probably get an end-system like the Schiit Yggdrasil when it becomes available.
So, you don't consider STAX to be too revealing to enjoy relatively poorly recorded genres like Rock?