Cowon players, while most of them are powerful enough to power IEMs such as the SE530, still don't do the best job possible when compared to being couple with a good portable amp. I used to think my D2 sounded wonderful with my SE530 and Atrios, but after I added the Tomahawk, I was astounded by how much better the SQ got. It was much cleaner, more refined bass, treble and mids, all around more controlled. It also got rid of the sibilance, and increased the somewhat narrow soundstage that Cowon players are known for. And while doing this, it stayed very transparent and sounded completely natural, and didn't color the sound at all.
Now with the Predator, it just gets better. Just to clarify, the amp in the Predator is far better and more powerful and controlled than the one in the Tomahawk. While the Tomahawk was already an awesome amp that was comparable to the Hornet in sound quality, a burned in Predator I've been told by many sounds almost like an SR-71 amp, and in cases even like a desktop tube amp. So you're NOT just paying more for an added DAC when buying a Predator, but an amp that can drive most cans in existance with little difficulty.
The Predator, size-wise, is pretty much the same length and width dimensions as my D2 (and almost as light), so it's actually pretty cool when I want to stack them on top of each other.