Don't get me wrong, perfectly fitted W3 sounds absolutely sublime...
I get perfect fit and seal if I use Atrio's triple flange - but the fact that its fat body makes my ear very unconfortable after 20-25 mins.
The bass should be big, but tight and punchy, think of TF10 but much more refined - IMHO
man i wish i could get used to those triple flanges. just cant stand the things!