An X1! If you're still using the stock cable: dump it. The cable is high resistance (1.8ohm)! (Get a V-Moda Audio Only Cable to replace it.) See more on Tyll's review @ InnerFidelity: http://www.innerfidelity.com/content/big-bottom-and-lively-top-philips-fidelio-x1
Beyond that, I didn't find much of a difference between the DACs (the WM1811 is implemented pretty well in the N2). For me, I had to change players. I loved Poweramp for its features, but I found its sound quality dull, flat, and unengaging. I used it forever though because I just couldn't give up its UI.