I was at the Chicago Head-Fi meet yesterday and Jude attended and brought the Chord Dave and Cavalli Audio had sent a Liquid Gold. While I throughly enjoyed the pairing, I am now sitting at home with the Liquid Carbon paired to my older Meridian 808.2i using a Vero Full-range cable paired with my HE-6 and I am not missing the Gold and the Dave.
From what I've heard from others (and what I heard myself), the Liquid Carbon doesn't drive the HE-6 to its full potential. It's capable but you're leaving performance on the table. The LAu, drives it better and it sounds better because of it.
Don't get me wrong... if you're not hearing an improvement from the $600 LC to the $4k LAu, then you're lucky in a way. I had to send my Crimson back to Cavalli for a bit because I borked something (user error FTL). When it was gone, I was perfectly content with the LC. But getting it back, was a nice improvement.