Hello and welcome,
I am currently working on a 2x65W amplifier shield for Raspberry Pi, which should be available this month. Additionally, I am also working on a well-designed box with a built-in amplifier 2x65w in the spirit of the MN cast so based on ESP32, which should be available in three months as it is more complex from a mechanical standpoint.
Regarding your question, if your Proto reboots, it is likely due to an insufficient power supply that cannot absorb peaks. One solution is to try a 3A USB charger or higher, or even better, connect a battery to it, even if it is plugged into the USB, as it will act as an energy buffer. Additionally, the impedance of your speaker is important, and the best results are achieved with 4-ohm speakers.
I assume you are using Squeezelite. Be sure to have the GPIO gain set up to pull down in the config to achieve the highest volume.