The Mac is very flexible, and quiet for a computer.
For 2 channel music, as a cheap start you can use the optical out into the G68 if it has one (I get confused on what each model has). The next step up would be the Halide Bridge although I haven't personally owned one which would use an SPDIF input. I went for the Weiss but to be honest it was based on online reviews, I haven't directly compared the Bridge and the Weiss, but FireWire makes a lot of sense. I then use Pure Music which means I can use FLAC files easily, and has good quality upsampling built in. If you have an iPhone or iPad you can then use the remote app to control it.
If you add a HD621, you can then use the Mini as a movie server as well via HDMI. I use Plex as a front end which is incredible considering its free.
You don't need to buy the latest Mac Mini either, for a cheaper way in, use your favourite auction site to pick up the previous version, for music/film servers the older ones are just as good.
Ultimately, as I said before, I know I will end up with Sooloos because it's Meridian and they know what they are doing; you have to remember, in real terms, they only took them over fairly recently and it takes time to get things sorted out. But things seem to be settling down. But, of course, it will cost more!