Mp3 decoding ranges from using VLSI chip VS1053 and the latest VS1063 along with a FAT32 filesystem on a micro SDHC card, up to the use of a dedicated USB-host chip like the Rohm BU9458.

If sound quality really is an issue; then consider using a professional setup with dedicated hardware decoders, controlled by a µcontroller or DSP.

Here's an example project with a VS1053 chip.

Our Webradio board WR1-AD uses the VS1063 as audio stream decoder.

	VS1053 SPI datastream MP3 decoder. Supports Ogg-Vorbis decoding. Stereo earphone driver.
	BU9458 USB-host MP3 decoder. USB 2.0 full speed host. SD Card interface. Supports MP3 and WMA decoding. ID3 tag analysis.

Custom FM tuner with MP3 USB-host and TFT touchscreen controller.