ahhhhh upgradeitis stikes the newbie
Welcome by the way....I wish I could help on this one, I've never heard the M50's but I know there is many on here we call the M50 posse that love them. I believe there is some differences slightly in sound. I don't like to use words, but I've heard some say the 50's are a little more laid back, and the 60's are a little more bright or forward.
Good Luck and hope someong else chimes in for ya
Randy
60's 150 350 4-Qs8's
Denon 2805
Sanyo Z2 Projector
Panasonic S97S