The 600's, and I assume the 650's, are very comfortable. I purchased a pair earlier this year and was surprised to find that I can listen to mine for 3-5 hours at a time with no ergonomic issues whatever, even while wearing glasses and working. I have also never experienced any ear fatigue, and am reasonably sensitive in that respect. They can be heard by others though at normal volumes in a quiet room.
If the latter is an issue, Shure's top of the line in-ear model is getting good reviews for sound quality, though I have not read anything about comfort.
If the latter is an issue, Shure's top of the line in-ear model is getting good reviews for sound quality, though I have not read anything about comfort.