Yeah, I was actually talking with Laxx about this after he let me try his E500. He supposedly needs different foam sizes for each ear, and he had the medium foamies on his E500. Those didn't fit my ears at all, and I had to use my Future Sonics beige foamies to get a good seal. Once I did, the E500 sounded great (if a bit analytical for my taste). I still want to try the Shure large foams. It really is a matter of best fit for YOUR ears. My wife, for example, uses the small FS foams with the EM3 when she's at the gym. Heh.
On a different note, I received my replacement Atrio m5 yesterday, a few hours after I'd mailed back the faulty one. Started burning the new pair in immediately (about 14 hours of burn-in with pink noise). Ahh... I love these things. They really do outshine the EM3 (which I uses yesterday) by quite a lot. Far more expansive soundstage, and not as much treble roll-off. The treble is a lot more relaxed than with the E500, but I really do prefer that. I *ENJOY* music with Future Sonics IEMs. Most other phones are just too analytical. Glad to have the Atrio back.