I love my M50. Great portable headphones. I'm not sure if there's better out there for the price, but I do know that they're quite amazing headphones, and I'm very happy with my purchase. I can actually hear the crappiness of the amp in ipod. Sounds so much better from my Total Bithead amp, which I could easily recommend as well!
I, too, bought them off ebay for about $90ish, I think.