I would not say muffled but the top end all around is not not quite as clear, detailed, crisp imo.
Between those 2 I'd have to say the MH1C is the better IEM the whole way around with build quality and sound quality. They have a cleaner sound with better bass impact and a better soundstage and imaging and the one thing the Mono's do better is they have a quicker bass response as the MH1C has a slower bass with longer decay times.
Much better fit as well but yes the sound is much more bass but not quite as tight although the Mono may sound tighter as the sub is no where near the MH1C imo.
I have Monoprice 8320 and a recabled Sony MH1C and i can say that MH1c beats MP8320 hands down. They are not in the same league for my ears. Whenever i want to listen to my other IEMs( RE272, GR01, X10) , I always end up reaching for my MH1C. the only IEMs that can share listening time with MH1C are the Vsonic GR07 trio( V1, MKII, Bass Edition).
I like your after pic but can you provide some more details on how it was done (products procedure etc.) or even video as a lot of people would like to do the same thing but do not want to ruin their headphones. Thanks.