There's no denying that the M50s are an excellent performer in their price bracket, but they get a lot of unwarranted hype here just because people who've never heard them parrot what others have said. I've owned the M50, Shure 840, M-Audio Q40, Sony V6 (predecessor to the 7506), and amoung those I prefer the Shures for their sound, or the Q40s when amped. Ultimately, I found them all a little lacking in one area or another and sold/traded them all and now have a Pioneer HDJ-2000 which I'm quite happy with, even though they're up a price bracket.
Since your guitar center let you try the M50s, they'd probably let you try some of the other ones as well. Maybe the M40s will give you near equivalent performance for half the price. Maybe you'd want to try a higher end Sony and listen to the 7509. Maybe a Beyer will catch your eye, or a good ol Senheiser will sway you.