I have now replaced the old cable with a HD650 cable. It wasn't too difficult. I was surprised, however, how thin the copper wires in the HD650 cable were. I'm not a very firm believer in the talk about how cables can improve sound (I changed them because the stock cable was too short), but still...the wires in the stock cable (which are copper color, btw) are a lot thicker, actually.
Another thing I was thinking about: when you "bypass the cross board", what you really do is bypassing the electret, right? That is, you resend the signal from the dynamic drivers to the electrets, and not the other way around, as in the original design. I don't know whether this is a good idea or not, but I guess it could be said to steal power from the electrets in favor of the dynamic drivers. It's weird that in all the discussions about this mod, I have never seen anybody reflect on this.