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 http://tinyurl.com/5rfmrz
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 *)