Upgrading to a turbo kit

Hey I have a 2000 A4 1.8t and I wanted to buy a bigger turbo, possibly one of the best, and the kit for it. I also thought about buying a turbo kit with everything already in it. I'm afraid that if I get a kit for it with a bigger turbo that i might blow something (injectors, pistons, etc). Whats the biggest turbo I should go? I got bout $3000 to spend so that means buying a turbo kit and getting it installed and still staying under the $3000 mark. I want some help so please write back and tell me what i should do. If i get a turbo kit I won't overboost, so ill just stay at about the 15psi range. Reply fast cuz i wanna get the kit soon.