Are the Fostex a big improvement over the Denon? What about vs. the HE-500? The open headphones worry me in an open work environment. How much are the HE-500 going to leak? Also, can the D1 drive the HE-500?
What's my biggest bang for buck upgrade option? Assuming headphones, but would getting something like the WA7 for the Denons improve things drastically over the D1 (I have my doubts).