I bought Etymotic Research ER4P-T MicroPro In-Ear Monitors years ago (for considerably less than the current £300 I might add).

The cable mine came with is annoyingly microphonic; they may have changed it, but I don't know.

Isolation is really superb and they are truly a reference in-ear monitor.

I find them comfortable, but everyone's ears are different.

Edit: looks like they have a new "reference" ER4SR.