I use my 1050 with a Mac DP G4/450s. I have it hooked up through an optical connection using a M-Audio Sonica. It works really nicely when playing tunes off of iTunes. I had some issues trying to get the surround sound feature of the Sonica to work properly but that's more of a software than a hardware issue. The Sonica connects to the Mac using a USB connection.
If you hook up the 1050 to the iMac using the regular stereo 1/8" out to a RCA Y, the only issue you may run into is a buzz due to the unbalanced connection. Other than that, it should work ok.