These are terrible without an amp. And even with an amp they are boring. They are also very uncomfortable and I've never had a seriously uncomfortable pair of IEMs. I doubt I'll even use them enough to find out how bad the build quality is. I'm sticking with my Etys.
make sure you experiment with different tips. these suck with the wrong tips. I hate the bi-flange tips they instal on them. go with a nice single silicone tip that fits snug. then see what you think. these IEM's are very tip dependent.
Do you really think that Etymotics are more comfortable than the RE00? Which one do you have? I have a MK5 and I barely use them because of the comfort issues and they are the most uncomfortable IEM I've ever used.