well what do you want to do with your car? if u want to drift you should go with the sr, but if u wanna drag then i suggest you stick with your ka.
If you wanna make the KA faster then just turbo it, but i recommend you get a intercooler and a air filter first. Doing this will also let you have more boost (more psi). to control the psi get a boost controller.
more experienced members will proboably give you better advice.
hoped that helped
