The Raspberry Pi doesn't really have a proper audio interface. What options are available to give it one? This is a list o I2S-based Raspberry-Pi-compatible add-on boards (HATs) that also provide amplification, so you can directly connect at least two speakers.
- IQaudioIO's Pi-DigiAMP+
- Allo's Piano 2.1 HiFi DAC + Volt AMP
- LOCO DAC AMP
- Collybia's Mamboberry HiFi DAC + external amplifier
- HiFiBerry AMP+
Possible sound improvements
- Allo's Kali stabilizes the bitstream, got a good review by VolumeIO and elsewhere.
- Allo's Capacitance multiplier (but this could be anything to stabilize power supply).