Well, the problem is that I don't (yet) have a preference
.
It's not possible to buy anything non-sennheiser in my country and I was planning to use my business trip to get something better than cx-300 I've been using for the past few years. Good bass sounds great, I'm just worried that they will be too bright for my taste and genres I'm usually listening (well produced prog-rock and badly produced metal/hardcore). Well that and that 4001 will not be much more expensive and they'll kick 2000j's ass. I'm pretty sure that I will not be able to sell them to anyone here, if it happens that I don't like them.
I did similar leap of faith with X2 (never heard anything similar before) and I'm really satisfied with them (my brain adjusted to grainy treble).