Funny that you mention the M6, because those are my "throwaway" pairs! I have about five pairs of 'em that I throw in my bag whenever. These M2 are pretty darn good for the price, though.
Have you tried the M2? I'm in for a pair. M6 as throwaway -@ $19 bucks a pair
I have more expensive headphones, but love the M6! Only bud style that stay in my ear.