Listening to Music. That's all you really need to know. :)
I have built my own 4-way crossover 5 foot speakers & love them to death. Using a design from a friend of my father's that sells for over $15K on the open market. I can tell you from experience that while the profit margins might be high, the materials alone in high-quality kit also takes a substantial investment.
Ultrasone PRO 750's, PRO 950's, PRO 2900's, various others. Love Ultrasone. Dr. Koenig is also very easy to talk to as well. I appreciate when the designers aren't so aloof as to shun talking to lay folk. Also, AKG K701's in passing, as well as a variety of inexpensive IEMs.
Headphone Amp Inventory:
Meier Audio Corda Classic. Had CIA amp - hated it and sent it back. Bought some other cheaper amps as well. I think I literally ended up throwing them away or donating them. Also have some half-way decent amps w/ dedicated headphone out connections but... they of course have limitations.
Onkyo C-7000R (statement product). Old Oppo universal player (not so universal anymore :)). Sony NWZ-X1061, Sansa Clip+.
BJC LC-1 + whatever came with some of my equipment. Sony has special active noise cancelling head phones that are not easily replaceable, for example. Stock power cables. Not ready for the custom power cable insanity.
Brickwall/Zero Surge protection
Other Audio Equipment:
Some other Onkyo stuff (I really like them for the price).