AKG Acoustics K1000 Headphones

Anyone tried these? They're pretty pricey [about twice the cost of Sennheiser 650's] and it appears that they have to be driven by a low power amp, not a headphone jack or a headphone amp. I'm curious, because most people talk about Grado or Sennheiser cans.
I use a pair in my office regularly. They are an awesome phone, if you can get past the quirky (bizarre?) looks and ergonomics. They work great with Cary 300 SEI, Cary 2A3i, Audiovalve RKV, and Granite Audio Aspen amps (as well as many others). Very revealing, need good source and amp, but very rewarding. No isolation but most speaker-like sound of all the cans I have use.
I've heard a buddies pair at his place several times. They are very dynamic and detailed, very open for headphones. If you have a big noggin they can squeeze the bejesus out of you. I didn't want to stretch my friends band, I'm sure it could be improved. As Swampwalker mentioned, the AKG's offer zero isolation. They stick out from your ears a bit, and can be heard by others in the room. You'll need to drive them from speaker taps. I've tried them with a Sonic Impact which paired quite well. While I enjoy these, I can't say I prefer them to the 650's driven by the same amp.
I listened to these once and found them to be one of the most unique and detailed presentations of the music that I had ever heard.

It still intrigues me to this day and I will buy a pair when I can afford it.

If you prefer a very rich, warm sound then these are not your headphones. On the other hand, if you appreciate crisp, detailed sound then these are just the ticket.

Good luck,