As far as the differences between the FA-4E & 846, the Shure is more dynamic in terms of bass extension. I get a soundstage which is a little bit wider, and treble extension with about the same ultimate reach, but this is only the case with the most ideal tips. For me that is Sony Hybrids. I have to wrap a little bit of clear tape around the nozzles so they stay on, but once in place they offer notably more open sound than any other tip I have on hand. Vocals on the FA-4E are a touch more distant (but nothing of note when not listening directly after the Shure). On the 846, they're a bit more front and center.
Overall because of the bass I enjoy the 846 better. But the FA-4E is very close in the rest of the picture.