I have RE252, which is a cousin of the RE0 (not the same, of course) and I can say that the ADDIEM, with the right tips/fit, are excellent in-ear phones for the money (esp the $35 ebay price), so I can see how that incremental difference doesn't seem worth it. Many of us have experienced the same thing when we believe we are moving up in the IEM world. I've owned the IE8, UM3X, W3, Image X10 and now have the TF10 - all top tier phones. And while they were all good in their own way, in my view no way do they justify $300+ price tags compared to today's emerging breed of sub-$100 IEMs.
Anyway, I understand your situation. My guess is the RE0 would benefit more from amping, but if not using an amp/LOD, I also can see how the difference doesn't seem worth it. Maybe burn-in will change the RE0.
Example: Because of a review by Joker, I bought a pair of the Cyclone Storm PR1 Pros for $50 on ebay. I like them so much (he compared them favorably to the RE0, with a little more bass) I bought a second pair (they were $40 this time, but haven't arrived yet), and they are not far behind any of my top-tier phones. That is no BS. With Sony hybrid tips, they sound fantastic.