I saw your post in HeadWize and responded there too. The only place to audition here is AudioFX on Howe Ave. They usually carry the entire Grado line and will let you audition for hours. I spent 2 hours with the 225s and 325s hooked up to an Arcam system with my CDs. They gave me a chair and left me alone. I bought the 225s.
They also carry Stax, but I didn't see any in the showroom. Another place is Paradyme Sound on Fulton. They used to carry Sennheiser, but the times I have been there, they had none to audition. Good Guys carries Sennheiser as well, but not the 580 or the 600.