i would definately jump straight to the e4c's, i wish i had. i went from sony stock buds to ex71's to md33s to e3c's (which just dont sound musical to my ears, all mids and nothing else, they just seemed... well, sterile) and now the e4c, which sound awesome. to answer previous questions, yes you can sleep in them, with more comfort than the 2c or 3c, not that i would reccomend it. and yes they come with a very good quality case. the build quality is the best of the 3 in question too.
so buy the e4c, then never come back again.