KKK Turbo Interchangeability

I'm looking at buying an Audi 200 Quattro, which has the same 2.2L 20v 5cyl turbo motor as the 1992-1995.5 Audi S4/S6s. They use a KKK K24 turbo, KKK part # 5324 970 7000. After driving the car, the turbo seems a bit tired(190k miles), and I was wondering if I could put a bit bigger turbo on it to get a little more power out of it. Stock power is 217, but I only saw 1.2bar absolute pressure at near full throttle. I'm guessing the turbo is only making around 4-5psi max, power is probably around 180hp now. If I can get a slightly larger turbo, such as a K26, that'll bolt on(I don't want to do a lot of work, got enough projects as it is), I'd like that. I'd be happy with just having the stock power back, but I figure if I'm replacing the turbo anyways, might as well go a bit bigger and run a bit more boost, get 235hp out of it and give my dad's brand new Audi a run for its money. I don't want to replace anything besides the turbo - replacement turbo must bolt up in the old one's place. I will run a manual boost controller on the stock internal wastegate. Thanks guys