[prisoner6]

Sold my Denons and looking for something new for my iPod at work.  I have heard good things about each of these.  
 
Assuming a similar price, any thoughts?

 

[ljokerl]

Depends on what you're after - the S4 has big bass & big treble, tends to sound aggressive, and struggles with smoothness and refinement. Lots of people like that though. The SF5 has forward mids and is a bit rolled off on either end, tends to sound more relaxed except for vocals (can be very forward), and has trouble picking up microdetail due to smoothness. I'm guessing the SF5's sound signature will be the less popular of the two out in the real world (i.e. outside of head-fi). It's a lot more complicated than that but those are the first things that come to mind when I think of either one.