Nothing to add really, but to say that the S with my sr-71 is the greatest thing in the world...the bass is perfect. I have some Senn 580s at work and I never use them.
I'd say if you're used to the Ety bass with the P than you should be amazed by what the S can do. You are ready.
Bass is a big debate amongst head-fiers I think,...but I'll take the mature bass of the Etys anyday!!
I can no longer stand bloaty, humpy, eardrum-pushing-bass going at all times. Only when necessary. Like any ingredient, especially one as powerful and dominant as bass it should be used sparingly. ER-4S has it down.
I remember a long time ago I realized a strange phenom when I had the good sense to turn off the "Bass-Boost" on my portable boom-box thing...I actually noticed more bass. In reality I think it returns the punch of the bass to the proper frequency. That is at the bottom, rather than the mid. My God, everything started to sound better. Treble...mids and yes the bass.
Phh...bass boost...I think about all those silly teens with their rap music rattling their cars on the street. I don't know, but I don't think that's added for the music. More like some urban mating ritual...like a peacock and it's feathers, or something.