I haven't heard any changes in the sound from my SHL5. I've bought them new last June and played them intensely since. The main changes I heard were with amplifier's matching. I had the chance to try them with Luxman L-505u, Sugden A21al, Nelson Pass "The Zen" and actually Luxman L-590AII.
About single wire, the owner manual suggests to connect them to the lower posts.
By the way, Merry Christmas to all!