It’s good that you know that, what you heard was not necessarily an upgrade but, a different signature. Many times we hear a different sound signature and, we end up thinking it is an upgrade. For me, an upgrade means a noticeable improvement in the technical capabilities of the IEM, without making the IEM sound bright, to give an impression that it has more clarity. Given that our brain can be easily tricked into believing that, the new IEM is more clear, or having more details due to brighter sound or thin notes, I have started relying on other technical aspects such as: instrument separation and layering, transparency and timbre(how natural an instrument or vocals sound), soundstage and imaging.
Law of diminishing returns kicks in hard once we cross the $300 range. My tape-modded IE80 and the U10 and U12 share many similarities, and so the improvement I perceive on my A10 is because, I know my IE80 very well and I can pick those fine nuances in tracks that I know does not exist in the IE80. If I were to ask my wife (who is not into headphones) to blind test an IE80 and U10, I am sure she may not be able to tell these apart.
I was also considering Angie initially. Until I came across a post in this thread a few months back, where the poster said that, to him/her, the U12 was better than the Angie and ended up selling his/her Angie. I have read great many things about Angie, especially about its Mids (Vocals in particular) and I hope to try it someday. I have not tried too many TOTL IEMs, but few members who have tried many TOTL IEMs, say that the Mids on the U12 is special. After comparing the U10 and the U12, I preferred the Mids of the U10 as I found the U12’s Mids to be on the thicker side for my tastes. I guess it all comes down to personal preference. I highly suggest you to try and demo before you make your purchase. Even if that means waiting for a few months or taking a trip to a Canjam or Rocky Mountain Audio Fest. For all you know, you might end up liking the Angie more.
My U10, U12 comparison:
http://www.head-fi.org/t/739712/1964-ears-adel-iems/4665#post_12489190