Thanks for reply. Looks like it is simpler than I thought.
Mac Mini Plus would be nice, but I want to try Sonos solution. At the moment I am not worrying too much about the sound quality. For serious listening I can use my BAT vk60/vk30 with Tyler speakers. (I don't listen to digital music that much, mostly vinyl with BAT ;-)
So, with Sonos, I only need to purchase a Sonus Bridge and Connector, about $400 in total. Since the Sonus connector has an analog output I would not need a DAC, well at least until I feel bad about its analog output sound quality.
Then, I can use my iPhone or iPod touch to control the music until I get an iPad.
I also see wireless receivers (amp + tuner) are coming to the market). The receiver can recognize music files stored in a wireless hard disk. But I am not sure whehter they support controls from iPhone/iPad.
Many thanks for your input.