Well, then I'd say... don't let yourself be bothered by E12 for long. Just be content with BH.
In case you ever need more midrange and bass quality, and you want to reduce treble glares, E12 is just right there.
And the C421 is now discontinued. You can find it used on the market for approximately $130, so it is now unfortunately in the same ballpark as BH.
I am anticipating purchasing the E12 once the revised bass units are available in the US. Regarding there significant power, do you feel the E12 has an advantage even with lower impedance headphones since the amp can be run at lower levels without being "strained" and as a result will run more cleanly?