The 500s aren't what I'd call balanced headphones. They have lower and upper mids emphasis (bump, not spike) that gives them a warm and romantic sound (perfect for voices & acoustics, IMO).
I could name a lot of cheaper headphones that are more balanced (Mad Dogs, HE-4, Q-701, ...).
The 5LEs are (much) more balanced, for the same price.
They're still available at head-direct but you need to contact them by mail.
the 5LE are still not balanced though, they have a slightly recessed midrange and a weird slightly buzzy treble.