Yes, but then one would have to support Apple through the initial purchase, and that's terrible.
How is it terrible? That would be like me saying "but then one would have to support Krell through the initial purchase, and that's terrible." Krell makes nice components, but would I buy one? Not for me anyways. Other people really get their jollies off of it. Mine would be an Anthem or McIntosh amp. Yum....
Apple isn't like Mon$ter cable in the sense that they sue or overcharge for their equipment (except the small stuff really); the difference being is that their market focus is different than the PC market, and that Mac has never had a profit margin like Microsoft does; they say it isn't a monopoly, but it really is by definition.
With that being said, there is actually MANY ways to go about using a receiver with computer. The Apple TV provides a pretty slim and cheap interface for pulling up music and video (but I don't know how well video support is right now on the homebrew side) as well as the Mac Mini (but it's $600).
An HTPC would also do nicely, but making it quiet enough poses a bit of a acoustical and thermal design problem; one of which I am working on right now to speak of.