Thanks again for all of the feedback, folks! I haven't used Weinmann side-pulls in a while but remember that between the lack of power and centering issues, I thought just about anything would be better. However, I also always used cheap brake pads and was using the older 500 series - I've read that the 605s were a bit of an improvement over that rather slender design.
I've got the 999s on another bike already and know I like them, so I might as well put the 605s on the current build for the sake of comparison and practice with getting them set up correctly.
Cheers!
-Gregory