And the T50rp's are almost worth $50. But they have been modified by various people to be quite excellent drivers, but for significantly more.
I really have to recommend trying something at a low price-point. If you're interested in the HD600/650, there's always the closed-back HD-280 for about $100. It's a good place to start. Senns have a reputation for being 'veiled', which is a snarky way to say that the treble tends to be rolled-off. But they are non-fatiguing and easy to listen to.
Grado's can be a killer entry into headphones, and the SR-80e is getting a lot of good feedback. I have the older 225i's, and once I bent the headband out a little and started wearing them more forward on my ear, the comfort has not been an issue at all.
Headphones can be a strange and addicting part of this hobby, and as you go up in price the differences can be quite subtle. I highly recommend avoiding anything over $100 or so when starting out