Yes, they do. Well, I do.
Jotunheim for my Sennheiser HD800s. Very satisfied.
Freya because I wanted remote volume control and source selection and nothing else. I find it transparent in passive mode, and a little more lively in the active modes. Nice product. And cheap!
Gungnir Multibit. I thought there was a meaningful difference when inserting the Gungnir.
Good toys, very fair price and they hold their value well, so you don't bankrupt yourself swapping things in and out.
Their store in Newhall is a blast, very nice folks.