lattesurf, The snug fit is a good part of the sound improvement as the sound waves are conducted through the jaw bone and ear tissue as well as down the ear canal which is why they produce such good bass tones. You can't actually wear the in-ear phones without the silicon tips because the mount is tubular so they will not sit in the ear.
Griffin also make earphones with covers like the ones you have shown called EarJams.
For 6 bucks what have you got to lose by trying them. Let us know what they are like if you get them.