Well, I find the HE-500 to be laid back, at least more than the 400 less than the LCD-2. The HE-500 has the better mids
of maybe both, though I'd probably argue with myself that the LCD's shine through more. They aren't recessed, so that won't be a worry.
The HE-500 is much more balanced than the HE-400 overall. But that might not be too important for you.
If not, the HE-400 is actually quite a good headphone and it does exceedingly well for the type of music you listen to.
I'd personally choose the HE-500 over the HE-400 without a second thought. Though the differences aren't too much,
we all have different priorities in preference. Either headphone will suit your music taste very well.