dear JSPS:
thats hard to design this cicuit.because you want a high power output so i dont think u can find any IC's to do this for u.so u have just one way i think..u should make that with high power transistors and put some relays to swich in the input for different output voltage and u should always remember the maximum COLLECTOR and EMMITER voltage and also output CURRENT that is transistor's POWER.u can use a simple rgulator for that..i hope u can make that if not should use swiching power supply