Glad you like the 336. I had a Dark Voice a couple of years ago - don't remember the model. It worked fine as far as driving my HD580's, 600's and 650's. It just seemed to lack the dynamics I was looking for. But, for the price, it's hard to ignore. I finally found my ideal "cheap" amp with the APPJ 1502. It has its pluses and minuses, but it doesn't lack where it counts - for me. I've learned it's all about what sounds good to each individual - especially with headphones and headphone amps. When you find something that hits the spot, hang onto it.
Cheers