It's the Headbanger. I have one and, even if I don't like it anymore, I have to say that it's better than the headphones jack of my SL-SX500, which sounds very harsh on my MS-1's. The Headbanger has better bass, but that's it. In reality, I only keep it because the headphones jack and volume on my player are screwed up. I also use it at home with my PC, and sound better than the headphone out of my JBL speakers. I'll say it sounds like a good headphone jack, and that's about it.
But you can get something way better for around the same amount of money you can get a PortaCorda or a Total Airhead, both with crossfed, or get fellow headfier JMT to make you a very good amp.