This is what the setup looks like so far, without the LCD screen in place. behind the LED matrix is a Adafruit mic breakout board. I'll also be wedging a MSGEQ07 chip in back, with its associated components.

As for the blinky buttons - I've gotten those LED-topped buttons working! The HT16K33 is an amazing little chip - it can share LED pins with button pins, so it's only 9 wires to control 8 LEDs and 8 buttons!

I'm using a pretty minimal library for it, as I don't really need any fancy graphic routines for it. I was trying to get it using interrupts, but it's much easier to just poll it every 30ms or so in my code.