My aim is just that, what was stated above: to "put Messrs luisdent & gnarlsagan (and other Ety fanboys) firmly in their place, i.e. I'll be trashing the venerable and legendary ER4S". I think 200€ is well worth the price to get all those in this thread (and lurkers alike) to soon sell (or throw away) their Etys and eventually cause Etymotic Research to go bankrupt.
EDIT: Still curious about the "bass-head" filters.
This will be fun! But it's a shame I could have saved you 200€ by writing your review for you. "The ER4S is lacking any semblance of bass. The soundstage is claustrophobically small. And as for the fit, I might as well be jamming pencils in my ears; they might even sound nicer."
And the red filters are recommended. There is plenty of info here, including where to buy them and graphs from Rin. The effect is rather minimal, but the reds bring down the mids and some upper treble about 2dB. This sounds more accurate to me and lusident.