Car smps

Hlw am new here..and my English is not good

I want to build an amp like that of a car with 12vdc as input voltage

I just want to push a 100w amp for sub ( already made) and two stereo amp for mid and high i.e two lm3886 for mid and 2050 for tweeters

Can somebody help me a circuit for power supply that can supply over 300w

Any one with any suggestions