I agree completely with most of your comments above. There are a couple there that I haven't tried yet. Never heard of Ultrafinder; not sure if it is new or has just been way under the radar.
Your comments on X1 and Copernic are right on. X1 is definitely a strange company IMO; e.g., for a long time - until very recently - you had to use Internet Explorer in order to use their forum! And it seemed like Copernic banished all decent program development when they dropped their free search program. Once you had to start paying the bugs and poor UI appeared.
I did use Agent Ransack for a while, but kept forgetting that I had it installed and so rarely used it.
Presently I use mostly Everything and Windows Search on my computer. They get the job done... Kinda. But I still yearn for a good standalone desktop search program. (Think that's the first time I have ever actually typed the word "yearned"!)
I'll have to take another look at File Locator Pro.
I'm surprised that you didn't mention Archivarius in your post. That seemed to be a popular choice not too long ago, but I don't see it mentioned much lately.
I am very interested in what you said about Listary Pro in your post. I have been using that for a while but mostly using it for fast access to file locations when saving or opening files. I really need to bone up on the rest of its features!
My file manager of choice has been Directory Opus for the last four or five years. However since about a week before Thanksgiving Dopus has not worked for me. It apparently starts but is not accessible. My system has had a lot of BSODs lately and I just found out that it has a memory problem, too. So it might be my system that's preventing Dopus from running correctly, or it could be an issue with Dopus 11. (I've seen a few other users post about this problem on their forum). So I'll probably be addressing desktop search after getting my machine fixed and most likely reinstalling Windows on it.
Please pardon any typos or formatting issues in this post; I'm typing it on my phone since my computer is just about unusable now.