Sorry - can't help you with hiss questions on the B400. I have permanent tinnitus, and it masks any hiss that may or may not be present (I can't hear any). At 30 ohm, unless your source has an OI of +3-4 ohms, I doubt there would be much audible hiss though. MY kids couldn't hear any out of the X7ii at full volume with nothing playing.
I just got my Dipper back (loaned it to someone for measuring) - didn't realise how much I missed it until it was gone. I probably use the Dipper now more than any other IEM (for pleasure), and I ended up buying the review pair - I simply wanted to own it. The ME.1 is a very unique earphone. I liked its spaciousness. I have to EQ it for it to be enjoyable though. For me it is dissonant (similar to the Jupiter). That hole in the presence area needs filling. Once you've EQ'd though - it is very good.