Mike.
Give me a few days to listen to this setup before I get a sound review on it. There are a lot of variables at play here and I honestly don't have much experience with headphone sound, so I need to keep my mind open for a while before I make an impression. I know that a major thing holding this setup back right now are my cheap headphones. I'm currently using an old pair of Sony MRD-G42 phones, which are of the cheap around the neck variety. hopefully my Shure's arrive later this week or early next week.
What I have noticed so far is that SOURCE MATTERS A LOT in headphones, which is exactly why I brought the CD-X3 into play. Last week I was just using my Lenovo laptop's cd tray and windows media player as a source, and it WAS NOT CUTTING IT! Everything below 80hz was horribly distorted with or without the amp installed... it was just bad. The bass-line during the intro to John Mayer's 'Clarity' (from the album 'Heavier Things') was like tin cans full of rocks being rattled.
With the CD-X3 in play, the distortion goes away, but the bass presence and visceral impact gets lost a little bit.... is it the amp, the phones or the source? At this point I have no idea.