The earpiece and speaker distort the sound so much it doesn't really matter what DAC you drive them through. ARM microcontrollers tend to have built-in DACs tha

The earpiece and speaker distort the sound so much it doesn't really matter what DAC you drive them through. ARM microcontrollers tend to have built-in DACs that are probably good enough for that kind of use. But when you have your high-quality headphones on, you can certainly tell the difference between a $0.10 DAC and a $5 DAC, just as you could tell the difference between 8-bit and 16-bit samples or 22kHz and 44kHz sample rate. To get good sound quality, you need good DAC and audio amplifier chips and well-balanced circuitry around them. That takes space.