Has anyone posted a review about the W30? I've never had earphones before, but the W30 looks to be a great modern upgrade from my HD25-1 IIs. For earphones, I've considered UE900 (bad quality control), W4R (can't find new), IE80 (not enough isolation), ER4s (uncomfortable), and much much more. The W30s seem to slot into the correct price bracket and I'd probably pull the trigger if I knew more about them.
Don't just judge headphones by the prices and looks ;) All the ones you listed have a different sound signature. If you search this thread, there was someone who posted their W30 impressions (if I'm not mistaken) so it can give you an idea how it compares to others. Going from 3 BA drivers to 4 doesn't guarantee more details but most likely will result in different sound signature tuning, so W30 vs W40 will be more than just $100 price difference. For example, UE900 will be more mid-forward with less emphasis on bass, W4R will be close but slightly different in bass response (as it was mentioned by comparison in this thread), ER4s have analytical/reference sound and fitment that requires a deep jamming in your ear canal, don't know much about IE90 though earpiece bass-tunning might give you a clue of the sound emphasis in those.