hmmmm, I had the Creative EP-630's once due to all the positive things people were saying about them and in my opinion, pardon my French but they were, how do you say? Shit!!!
I had got them for my train ride and I just went back to the wonderful Koss KSC-35 and dealt with the train noise with increased volume. I have heard the S4 and they both shouldn't be mentioned in the same sentence, the S4 are leagues ahead.
I have heard the S4's with thousands of hours of burn-in at Yodobashi and they sounded pretty descent, sure they didn't sound anywhere near how my SM3 sounds but I thought they were good for the price.
My advice, like others are suggesting is to burn em in, especially since they are dynamics.
They may grow on you!
I thought my GRADO SR-80 sucked when I first got them many years ago, they were my first Audiophile type headphones, after a couple of weeks I was loving them and hearing things I've never heard before.
Give the S4 time!
And Happy Listening! 