I have the 911s and love them. They are my favorite/best sounding phone. I like them better than my Etys. I have never heard the 931 so I can't compare the two. Many people complain the 931 is too bright. To me, the 911 is not too bright but they are definitely brighter than my 770s. They have a nice extended bass (not as pronounced as the 770 but every bit as deep), the mids are great, and the treble is sweet. They are fairly forward sounding and very detailed. I have compared them extensively to the HD580, although some time ago. The 911 has better bass and treble with the Senns winning in the mids. The 911 has a more forward, lively sound than the 580 and are more detailed than the Senns.
The only official review i read about the 911 was shortly after I bought mine. The reviewer preferred the HD580 sound and said the 911 sounded too detailed and was not as much fun to listen too. Good thing I bought them BEFORE I read his review or I may not have bought them. While I agree with his comment about the detail, I think they are a lot of fun to listen to. I especially like them with classical and jazz. Chamber music, in particular sounds awsome with the 911. They also rock pretty good and are great for vocals.
If they are in good shape, $100 is a great deal. Are they still in the box or are they used? I bought mine many years ago and they came in a nice aluminum case with molded foam insert. The case even has a lock and key, kinda cool.
If you get them, let us know how you like them. Sometimes I feel like I'm the only one who has them, or even heard them.
