I've owned the e2 for 8 months - constant companion to my iPod and loved them. I recently upgraded to the e3s. There are a number of threads with e2 vs e3 impressions by users. Just search on my nick with search terms 'e2 AND e3' and half a dozen will be returned like these:
http://www5.head-fi.org/forums/showt...ight=e3+AND+e2
http://www5.head-fi.org/forums/showt...ight=e3+AND+e2
http://www5.head-fi.org/forums/showt...2&pagenumber=2
http://www5.head-fi.org/forums/showt...ight=e3+AND+e2
My impresssions of e2 vs e3:
I find the E3 to be better in just about all respects. Fit better with new soft flex sleeves, sound better in terms of better resolution and clarity, better extension on the high end and tighter bass. You also have the option of using the tri-flange from Shure or from Ety as they both fit the E3. Ety tri-flange has a shorter shaft and I find that it takes some of the sibilance out of the highs that are present with the soft grey flex sleeves. I have not tried the Shure tri-flange. I mainly use the ety tri-flange and the soft grey sleeve which I find to be the most comfortable but not necessarily the best sonically. I like the foamies but hate the idea of replacing them or having to roll them to insert - pita.
I found the e2 closer to the ksc35 sound in terms of bass though they did offer a bit less clarity. Overall E2 are very good match for iPod and offer decent bass. The E3 have tighter bass but less punch than E2 and offer a bit better extension in the high end and overall better resolution and clarity - depends on what you are looking for in your headphone experience. I like fun, warm cans rather than boring and analytical cans. I like the bias both the E2 and E3 impart to music and don't really enjoy very analytical cans though the E3 move you closer toward the analytical due to the better clarity and resolution they offer. I never found the vocals to be muddy or muffled with the E3 but perhaps my perception simply differs from others here.
The clear flex sleeves never really gave me a good fit nor did I find them very comfortable - one of the main reasons I moved up from E2 to E3 though I did perform a sleeve mod on the E2 to use a Sony mdr-nc11 sleeve (same or similar sleeve to the EX70/71 I believe) and this is comfortable. These sony sleeves are very similar to the soft grey flex sleeves that come with the E3.
Sometimes I miss the bass punch of my E2 but overall I prefer the E3 as I wanted better clarity and resolution and comparing them side by side there is a noticeable difference.
Are the E3 twice as good as the E2? That's a trick question. I don't believe that you can make such a comparison in those terms. Once you get to a certain point with good cans, you are comparing subtle differences. Are the subtle differences worth the extra cost? Only you can decide for yourself what you are willing to pay for your listening experience and if the differences (gross or subtle) are worth it to YOU.
Best bet is to talk with some of the forum sponsors like Todd the Vinyl Junkie and see if they will offer you an audition. If this is not an option, then you may want to try them from a vendor with a good return policy. I only recommend this if you are serious about buying them. Vendors who offer return policies are in business to make money and should not be taken advantage of for the purpose of "renting" out product if you are not serious about making a purchase.
I may be auditioning the E5 and the Ety ER4 in a couple weeks too just because I'm curious - no one can make up my mind for me and no one should make up your mind for you - try them yourself and see.
I hope this helps.
