FOUND IT! I knew this before from using Gentoo, but too much time elapsed between then and now. It is never a good idea to have many use flags set when emerging large packages. In this case, I applied "kde" and "kde-plasma-5" mix-ins to my epro before I had X working.
I fixed the issue by removing both mix-in flags, and then doing what still needed to be done to get a working X. THEN I re-applied the kde and kde-plasma-5 mix-ins, and, really, life is good again.
"Emerge --sync" didn't help, had to mask the package. (My Gentoo reflexes are rusty - shoulda thought of it at first!). KDE is installing without a hitch now. Thanks!!
