today i received the module
while plays mp3 files without problem and with a very good quality, i can't play wav files
tested 8bit 80kbps 22khz without success 
something odd: if you want to keep the files order, firse must create the mp3 playlist on hard disk (0001.mp3, 0002.mp3, ecc) and when ready copy to the micro-SD card. If you rename on microsd card it will messy the order.
I used 2 watt stereo speakers @ 8ohm: if used in mono no problem, when stereo you can hear clipping. With a mini amplifier no problem at all also in stereo mode.
const int buttonPinFire = 7; // FIRE
// variables will change:
int buttonState = 0; // variable for reading the pushbutton status
void setup() {
// initialize the button pin as a input:
pinMode(buttonPinFire, INPUT);
// initialize serial communication:
Serial.begin(9600);
Serial.write(0x7E);
Serial.write(0x03);
Serial.write(0xA7);
Serial.write(0x1F); // volume max
Serial.write(0x7E);
// start sound
Serial.write(0x7E);
Serial.write(0x04);
Serial.write(0xA0); // A0 for SD card
Serial.write((byte)0x00);
Serial.write(0x02); // track number
Serial.write(0x7E);
delay(3000);
}
void loop()
{
buttonState = digitalRead(buttonPinFire);
if (buttonState == HIGH) {
Serial.write(0x7E);
Serial.write(0x04);
Serial.write(0xA0); // A0 for SD card
Serial.write((byte)0x00);
Serial.write(0x01); // track number
Serial.write(0x7E);
delay(300);
}
}