It will control the receiver's volume level regardless of which source you select. If you connect a MacMini to your receiver and selected as source - sure. But it will not allow you to switch sources using a remote.
The way it works is it attenuates the signal that passes through it. So if you put it in a tape loop, it will work as long as the receiver is in "tape monitor" mode, but will control only volume, and generally only down from the level physically set on the receiver.
There are similar devices that have more than one input and additional source selector function. I have one, I described it here
http://www.audiokarma.org/forums/showthread.php?t=636579
(and no, I'm not selling, no affiliation to the manufacturer either). A few similar VC boxes others found are also mentioned in the thread.
Thanks! I'll check out the thread