A big thanks to everyone who has responded positively to the pictures of my modding. That's really encouraging--especially since I felt like I'd probably half-assed it all, and this was my first-ever attempt at this sort of thing.
A little follow-up on my thoughts re:sound signature. While I cannot state empirically that this is all due to the mods, these things sound HUGE! I mean, the soundstage and energy to my music is just unreal. Prior to purchasing my HE-500s I'd read a few reviews where people made claims like "I've never felt this close to the music before," and now I totally understand what those people meant. Even with my eyes open and while paying conscious attention to my kids, or while reading a book, I am constantly blown away by the immensity of the HE-500s' presentation. Listening with my eyes closed allows the entire world to melt away from me, leaving behind only the music. The sound is also so unbelievably clean and detailed from one end of the spectrum to the other that I can listen at absurdly high volumes for four-plus hours on end without even a hint of fatigue.
For those on the fence, if you already feel this way about them in stock configuration then don't risk the mods; however, if what I'm describing escapes you then I wholeheartedly suggest you dive right in and treat yourself to the "real" HE-500 experience. I cannot imagine how anyone could ever regret this.
In a word, it's perfect.