To be honest, I think if you are going to be upgrading from the EP630, you should go straight to at least the Shure E3c or E4c in order to hear a worthwhile difference. It's worth paying the extra.
I went from the
Sony EX71 (Used this for about a year before being a member of head-fi.org, I thought this was the best sounding pair of earphones in my whole life
)
Etymotic ER6i (Wow, so detailed but the lack of bass leaves me wanting more. There is bass but I have to listen carefully in order to hear it)
Shure E3c (Rolled off highs, I prefer the ER6i)
Shure E4c (I upgraded to this from the E3c, the best soundstage I've ever heard in an IEM. The stereo imaging is amazing. As good as my ER6i and sounds more natural. The ER6i just seems to exaggerate the high frequencies and transients to an extent that is is ear piercing and fatiguing to listen to. I can see why people like the ER6i though, it is a very detailed pair of IEMs for its price.
Listen to "Royksopp - Triumphant" where you hear the cymbals and you will see what I mean. The Shure E4c controls this harshness very well, it is more pleasing and natural sounding to the ear IMHO)
Shure E500 (Should arrive today, I will post later about my experience with these babies)
What are your listening habits? Do you just need earphones for on the go? Are you very critical when it comes to sound quality?