I bought my first pair of these when they first came out in about 1986 or so and have been using them for portable audio ever since. first with Aiwa Walkman tape players and now iPod Classic 160.  I have gone through a number of them since then, but the great thing about Koss, no matter what you may think of their cans today, is their lifetime warranty.  If the cable shorts out, or they otherwise break, or become unusable, just send them back to Koss with a check for $7.00 and they will fix (maybe replace).  Used to be $5.00.   Check with them for the current repair rate.   I've bought a few more pair, had several repaired by Koss, and been using ever since for portable audio.  Great value, great sound for the bucks.  I've just bought some B&W P5s, so maybe I will have something better to wear outside, maybe not.  Who knows.  A definite bargain.   Currently about $35 on Amazon.

I purchased this unit to replace my previous 3930 which began acting up; HDMI output began functioning sporadically, then CD functions began failing, tracking and other audio noises.  I had replaced it with an Oppo 95 which I found to be bass shy.  I want all my low frequencies, so I found a brand new unit on Ebay for $400 +15 ship.  My previous unit was a refurb which lasted almost 2 years before trouble set in.
That one was $400 also, so either I am lucking out with great deals on players, or paying the cost of replacing something acquired at a bargain.  Depends on how you wish to look at it.  Original list was $1500.
 
There is no contest.  The Denon is the machine I use when I put on the cans, the Oppo is for watching movies.  I occasionally use the Oppo for SACD 5 channel output with the speakers, but for phones the Denon is the one I prefer.  All the bass is there, not like the Oppo which has diminished output below probably somewhere around 100 Hz.  I am guessing here, have no way to measure.
 
The 3930 is simpler to set up, just run a cable from it's stereo SPDI/F to your amp.  With the Oppo you have to navigate submenus to get the right output for phones, although the way to decouple it from Pure
Direct is sometimes confusing.  Have to memorize this stuff.
 
If I am lucky, I will have a machine I am happy with for a long time.  If not, I will probably have to start saving up for something that costs a lot more, or else get lucky again with something new and affordable.  

Overall I am very happy with my Oppo 95.  We are not reviewing this stuff here on this site for the video performance so I will skip that.  My only complaint is that its audio output is bass shy.  I bought this to replace a Denon DVD-3930CI which I finally had to give up on.  After listening to the Oppo for awhile through Creek amp and HD600 cans I just couldn't accept it as a suitable substitute for the Denon, so I was lucky enough to find a brand new Denon on Ebay for $400.  I may occasionally listen to the Oppo through speakers, or as a 5 channel SACD source, but my heart is with my Denon. 
 
Easily competes with units much more costly and the video performance is without fault.