All the stuff you mention will help with the handling department, I wouldnt want to go 20's as your ride will be less compliant not to mention depending on the set of aftermarket rims you might dent it on potholes, I've done that twice with my old matey Yaris. I would rather go 19's or even 18s with 'wider' set of tires for improve grip. This aligns well with your suspension mods. On a quick note, you will want some good quality rubbers to go with your mods. I've drove my old man's Kluger on Maxxis rubber and I can honestly tell you they are rubbish.