So when you booted into KDE, with Energy Star stuff in KDE's Control Panel turned off, what does the output of xset -q
Perhaps KDE or some other stuff re-enables DPMS along the way.
So... just let's make sure it is turned off again by adding it to some other random places... :-/
Let's create a simple shell script in ~/.kde/Autostart (or whatever folder you set as being the Autostart folder).
xset s off
Be sure you made it executable with chmod +x DisableDPMS.sh
(Oh dear, I hope that helps. If you sometimes get that feeling that in Linux one has to invest far too much time in some trivial things, I sadly have to agree...
but "this other OS" has its own share of problems, too, I guess.)