The Pi itself doesn’t drain much power. It is suggested to use a 2.5A power supply to utilize the 4 USB ports. A PIR sensor or a microphone consume close to no power. So I am pretty sure 1A should be enough already. I know in my case the Pi drains 560mA at max, running MM (using WIFI, USB keyboard dongle, temperature sensor and PIR sensor).
I am using a 0,20€ 3A buck converter for my Pi, which is powered by the 12V power supply for my LCD. Runs flawlessly for 3 months now continuously.