Mac or Windows

The Apple way is probably the easiest way as far as setup is concerned.
The Mac Mini is very popular as an audio source.
Of course it works very well in combination with other Apple products like the iPod.
You are a bit limited in choice of software, iTunes is probably the way to go.
Your hardware choice is limited to the Apple product range.
If you want to combine it with a FireWire DAC, your choice is very limited unless you don't mind using pro-gear.

Windows offers a far wider choice in software.
Players like J.River Media Center /Jukebox, Foobar, Windows Media Player.
Rippers like EAC or dbPoweramp
Taggers like MP3Tag
Etc. etc.
You have more options to configure the system to your needs but it will be more complex to.
You can choose almost any piece of hardware because that's where Windows is about, supporting each and everybody's hardware.

You can choose from a wide range of sound cards (if you have a desktop).

Discussing differences in sound quality between Mac and Win on an audio forum is almost impossible, in fact people trying to do so are often accused of trolling.
It is almost impossible to find unbiased information.
DCS is one of the very few sources I know.
They measured the differences between XP, Vista and OSX.
All can be configured to deliver bit perfect output.

This leaves one question unanswered: what about Linux?