Such an old thread, I heard that they have already discontinued this product but by far I have a love hate relationship with this iem.

SQ
It's fairly laid back but it's analytical
Bass is aplenty and yet it doesn't overpower the sub-bass
Mid is well articulated and highly detailed
Sibilance is high and transparent, need some time to get used to it
Soundstage is wide and warm and dry

Almost has no isolation at all, I've modified it with comply ear-tips and it's still the same.

VS XBA4, the XBA4 is more aggressive (but not as good as a W4)
XBA4's have a v-shaped soundstage EX1k is neutral or more like what an iem should be.
XBA4 is more isolated than EX1k
XBA4's mid in comparison to EX1k is almost world's apart, which kinda reminds me of SM3