Well, I went ahead and did it (installed Greenify and set it up) and as far as I can tell my phone is working fine. It's much less laggy, and so far Greenify has cut my battery usage in half. That's with heavy usage too- a lot of screen on time tweaking things.
Between Android Tweaker, Greenify, Nova Launcher (more lightweight than Trebuchet), zipaligned apps, smartassv2, 1.3GHz overclock, some Xposed modules, uninstallation of unused system apps and custom ROM apps, and better use of widgets and quick settings, I think I may have made my phone far less frustrating than it use to be. Time will tell, but I may actually be able to enjoy it now. Maybe I don't need new phone after all.