Components

Power supply:

This module does have separate 5V and 12V outputs. They are both rated at 1A. This is OK for our use case, because we will disable 2 cores and the GPU of the Orange PI board. So in my case I am alway way below 1A (about 500mA). The 2nd Voltage (12V)is used for the power amplifier board. Having an independent power source is very good because you will not get many digital noise at the output of the amplifier. So that module is much better than a 12V power supply and a step down voltage regulator. 12V 1A is also good enough for a normal room size since the digital amplifier is very power efficient
https://www.aliexpress.com/item/Green-board-12V-5V-full-Isolation-switch-power-supply-AC-DC-module-220V-turn-12v-5v/32473622268.html

Orange PI Lite

https://www.aliexpress.com/item/Orange-Pi-Lite-Support-ubuntu-linux-and-android-mini-PC-Beyond-and-Compatible-with-Raspberry/32662738571.html

Y148 Power Amplifier

You can also use other modules but I had this one already and found it to be very good.
https://www.aliexpress.com/item/Free-Shipping-1pc-digital-amplifier-board-Y148-15W-2/1336674190.html

DAC ES9023

One of the cheepest I could find but still very good sound quality.
https://www.aliexpress.com/item/New-Details-about-Wholesale-Audio-phonics-DAC-Sabre-ES9023-I2S-vers-Analogique-24bit-192KHZ/32709165070.html

OLED Display

Very small but very readable because of the resolution.
https://www.aliexpress.com/item/Wholesale-0-96-inch-4pin-White-OLED-Module-SSD1306-Drive-IC-128-64-I2C-IIC-Communication/32658908775.html

Rotary Encoder

Others will work as well if you already have some.
https://www.aliexpress.com/item/5pcs-lot-KY-040-Rotary-Encoder-sensor-Module-for-arduino-Free-Shipping-Dropshipping/32293140596.html

RCA Connector

https://www.aliexpress.com/item/Sindax-RCA-Panel-Mount-connector-RCA-Female-Socket-rca-Panel-Mount-Audio-Socket-Plug-connector-Bulkhead/32576650638.html

Power Switch

https://www.aliexpress.com/item/5pcs-KCD1-perforate-21-x-15-mm-6-pin-2-positions-boat-rocker-switch-ON-OFF/32662789727.html

Spacers

Just in case you don't have any this is a good set
https://www.aliexpress.com/item/120pc-M3-Brass-Spacer-Standoff-Screw-Nut-Assortment-Kit-Free-Box-with-Free-Shipping/2055128849.html

Case

The case is just a kitchen container I got from my grocery store. Since it is translucent the IR remote is working without a problem.

Jumper wires

If you don't have any
https://www.aliexpress.com/item/40pcs-lot-10cm-2-54mm-1pin-feMale-to-feMale-jumper-wire-Dupont-cable/32226515120.html