Your thread and experiences with the HEK played a large part in what had me worried about making the purchase.
I'm glad to report that I don't hear any of those weird car engine-like noises that you were hearing, and that my only build quality issue is the left cup swivels easily and the right cup swivels less easily.
Just out of curiosity, which headphones do you prefer the overall sound of over the HEK?
I prefer the HD800 over the HEK for classical, jazz, and acoustic, but then prefer the HEK over the HD800 for pretty much everything else.
Haven't tried an aftermarket cable for the HEK yet though.