Hey V4,
I'm with SS, in that they shouldn't sound muffled, but when I had my 262s, well at first yuck! and was also super doubtful that they would change aswell, and the only reason that I knew that they would was, that my first pair was bought second hand from the sales forum, and so they didn't need alot of play time to sound totally awesome!!! the second hand pair started out mediocre, but after 2 days of intense play time, and after I went to listen to them in morning, whalla! it was a night and day difference, these are IEMs that I can live with, kasweet!! and then the worst happend, just as quickly as I fell in love with the sound, the right side quit on me, AAHHHHG! talk about bummed, but I jumped thru some hoops and Head-Fi replaced them with a brand new pair, awesome customer service! and thats when I found myself where your at now, yuck! and wholly SH!T whats going on, man I wanted those second hand pair back!! but I got to working on them and slowly but surely these 150 imp IEMs started to come around! just like the first pair I had, they just needed ALOT of burn in time, I started getting satisfied with them after around 150 hours of use, I played them nightly with all kinds of funky stuff, some times at full blast, and listened to them during the day with what I like to listen to, and then when after they started to opened up, wholly cow! did they ever! and I fell in love with them! one thing that also helped in opening up the sound was modding the large bi-flange tips, I cut the bottom flange off and trimmed it flush, it helped with a better fit, and it seems like the longer stem of the bi-flange helps with the sound also, in fact although I no longer have the 262s, I sold them off after hearing the EX600s! I still use the large bi-flange tips and filters along with my 600s, in fact I've bought two more sets, and I no longer have to mod them, as my ears have enlarged and can easily accomidate them nicely! I hope some of this helps, happy listening!