really depends on your budget, source, and music tastes. The HD650s are the most expensive and tempermental. They need an expensive source in order to really shine. They have a more pronounced soundstage and bass....so out of the box, you'd find them good for classical, jazz, and electronica. The HD595s are easier to drive, are more versatile, and get more detail. Since they're a bit more upfront, they're easier to get rocking. They do well with most rock genres....especially classic rock and alternative.
I haven't heard the 555, but it seems there's camps that say the HD595 easily surpasses it....and others who say it doesn't. Since the HD595 can scale quite easily, though, I would say its worth it to start off with that.