L-P,
After a/b-ing the 5LE and the 500, I had a chance to pick up the HE-6. God willing, I'll try to post some formal impressions. What I've heard so far from the HE-6 is indeed excellent: greater LF and HF extension, more bass presence--not sure how I feel about that one yet--and what sounds like a a livelier midrange.
Swapped out the stock cable from the 5LE with the HE-6 cable, which has brought about a signal improvement to the 5LE's presentation: cleaner--much, much cleaner, smoother, more detailed and airy. Tonal purity is truly exceptional. Boy, do I like the 5LE! : ) [Listening to Toots Thielemans' Footsteps, the title track never sounded better.]
Also bought the Headphonelounge UPOCC recable (silver to ground, copper to ground). A preliminary audition suggests a capital improvement on the stock HE-6 cable.
pataburd