Hi Zimm,
Yes, the Grados tend to be very accurate, although I haven't heard all their models. Certainly the 125s are quite neutral and accurate, like your 80s.
Regarding comfort, everyone's head is a different shape and the pinnae (no smart remarks!)--the external ears--are also every shape and size (just ask Prince Charles!). What fits one person may be acutely uncomfortable to another.
There is a lot of interesting research going into manipulating "head-transfer" effects and equations to move sound outside the headphone or to simulate a 5.1 experience from two stereo speakers.
The reason that all headphones provide extreme separation compared to speaker playback is that when you listen with loudspeakers, the sound from the left speaker hits your left ear first, then travels around your head to your right ear a few milliseconds later. The sound from the right ear. . .etc, etc., so if you think about it, the brain interprets this crosstalk between channels and your ears as reduced separation between the left and right channels.
In ear-bud or headphone listening, the sound from the left and right channels is preserved and delivered direct to each ear, with none of the crosstalk between ears that occurs with speaker playback. Over the years, there have been a number of different speakers (Polk being one) and processors (Carver's "Sonic Holography") that included crosstalk cancellation circuits to correct for that problem in speaker playback. But those generated other problems. . .
Cheers,
Alan
