want to

Cheapest Apple thing is an AirPort Express. Uses itunes, but requires either a DAC and amps or SS receiver. Better options are Logitech Squeezebox Touch or Sonos. The DAC in the Touch is the best sounding. You will need an amplifier and speakers with Touch.

With Sonos, you can get their Play:3 or Play:5 These have everything you need including amps and speakers. These are the simplest one-box solutions.

Steve N.
Empirical Audio

Squeezebox TOUCH

Another option, although I have no experience with it, would be the NuForce Air DAC system. I believe the Touch will give you the highest quality of all the options presented so far. I just installed one last month, it works great.