Oh snap! I just typed in a rather lengthy reply about some of the differences, but when I pressed "Post Reply", it didn't show up even though the beginning of my reply can be seen on my profile under "Recent Posts". To make it short, what I wrote was basically that the B200 is more laid-back between 3 and 5 kHz, whereas the B400 is more in the background around 11 kHz. No major difference on the technical side, just some things the B400 does a little better in direct comparison. The B400 has got a softer treble compared to the B200 despite being less laid-back, giving it what some people would probably refer to as "analogue" sound.