you have a celica sx (australian for gts).
xs engineering makes a Turbo that puts out great power gains, but some people have complained of problems.
however, it won't have as much problems as a custom Turbo--they have more problems than i could count and i wouldnt recommened one at all.
if you want a Turbo, go with the xs Turbo, and now theres a strafford Turbo that's supposed to be excellent--you should check into it.
also, blitz is coming with a supercharger. it hasnt even officially hit the states yet, so i don't know how far off australia will be.