Thanks for all the details, Mlsstl.
Actually, I hadn't thought about the upper limit sample rate of the squeezebox until Sbank mentioned it. And I see you can get some files in 24/192 from hdtracks, so maybe I will consider another streamer.
When I first posted this, I was really only concerned about controlling the iMac over the PC-attached wi fi, and it sounds like I will be able to do that, regardless of the streaming device I wind up with. Not sure I'm too thrilled about leaving my iMac powered up all the time, but I guess that's a small price to pay. I can always walk upstairs to turn it on when I need it, but that kind of defeats the purpose of having hi fi available through wi fi. Might as well get a new universal player instead.
Thanks for all the comments so far. You've given me a lot to consider. If anyone's still reading, do you know if there are streamers that can accommodate 24-bit/192kHz?