Well this will just turn into a war hahha
If it were me I would look into the following:
I would look into the Brillelli 60
http://brillelli.com/brillelli_engines_009.htm It's more powerful then it's light. They also have awesome customer service.
I would look at the Taurus 3.2
http://www.taurus-engines.com/taurus_ts52.html These again are very powerful and very smooth running. Again greta customer service.
The others 50s you mentioned are great engines but I think these have them beat. DA is nice but known to have a slightly rough sounding mid-range and continous updates are needed. 3w50 is a nice engine but on the heavy side. Evolution 58 has had many reports of failed gaskets etc so far and its heavy as well.
Can't really knock the ZDZ 50 I havent really followed that engine.. but hav read a bit on. First 2 engiens I would really be my choice.
Best thing to do is start a search because everyone is going to say something different. I can tell you I dont think you will find a bad thread on either the Brillelli line or the Taurus line.
Hope this helps