My board, the ZB1, combines an ATmega168 with an XBee radio.
I burn the Arduino bootloader on the ATmega and use the Arduino tools
to program it. The pricing for my boards (ZB1) are at Loading...
If you decide you want to go that route and need five or more send me a private
email and I will be happy to go into more detail. My board is sold without the
XBee radio. The XBees are $20 each at Digikey or Mouser
The XBees have an embedded uC and are capable of digital I/O and analog input.
It should be possible to control LEDs with just an XBee (and a transistor buffer).
Playing the audio could be tricky.
(* jcl *)