If you're going to be using the headphone output on the Zune, it's not going to be superb. Keep the volume on the Zune about 3/4 of the way as the output will clip just like the preouts on a head unit. Sound quality from any player is going to depend on the format and the bit rate you rip at. From my experience, WMAs and AAC files tend to sound the best. MP3s lose a little. I use MP3s. My music is all 192 kbps in the MP3 format. I have an iPod touch that I use on my 800PRS. First of all, the iPod connection for the 800PRS is pretty slow. I've got another adapter on order that will let me control the iPod with the iPod, not the HU. Overall sound quality on the 800PRS with the iPod vs any other HU I've owned (mainly Alpine), is great. It's the least noisy adapter. The music is pretty clear, I can't tell how compressed I have it. If I play a CD then switch to my iPod, I can tell a difference, but if I get in my car and go straight to iPod, the iPod sounds great. Lastly, doesn't the Zune HD just have a higher resolution screen? Audio should sound no different between a Zune, Zune HD, iPod, Zen, or whatever MP3 player you're looking at, assuming bitrates and file formats are comparable.