Interfacing arduino with audio

Hi all,

So I've been experimenting with PIR and optical sensors to trigger audio files when motion is detected. I'm also sneding firmata to Processing. It works well so far but I need to get rid of the computer and just have the arduino and some shields as a stand alone unit that will trigger audio. The audio needs to be played out of Studio monitors so I need to have XLR inputs and outputs.

I was wondering if it would be possible to do the following things:

A) If I add an SD card reader can the Arduino uno load and play the audio rather than have it go through processing.

B) is there an XLR shield for the Arduino? Or can I just breadboard some XLR connectors and connect those to the Arduino? I need to figure out a way to have audio play through proper speakers, not just a piezo speaker.

I understand that there are voltage issues with this potential setup and I would appreciate any guidance or parts I could be pointed to. If a computer is needed I was thinking about integrating a Raspberry Pi, but I have zero experience with coding in Linux.