Start PC music Server from Scratch

Unless you actually enjoy fiddling with hardware you could simply buy a mach2music. If not at least you could look at their specs and use it as a guideline of what you are trying to build yourself. Keep in mind that ripping out the powersuppy and wiring the MacMini for external powersupply is not a DIY job.

You'll probably need a DAC. The Centrance DacMini is excellent.

I agree that the Centrance DACmini is great.
I have one.

But I moved it back to my computer desk top rig to play through my Audioengine A2s after I got the Schiit Bifrost DAC. The Bifrost is a better DAC: bigger soundstage, deeper bass, better articulation and detail retrieval, airier highs and more involving, for about $300 less. No headphone out, just a good old fashioned DAC that punches way above its price point.

The boards are swappable for future upgrades and there's a 15 day trial period with only a 5% restocking fee. It won't hurt to try.

You won't be sorry.

All the best,
Nonoise

I am undertaking a project of that sort myself, though using a 64 bit windows platform. My focus will be on the computers performance as well as isolation, noise, emf/rmf insulation, as well as an internal (better than external) solid state dard drive (a few, probably). I am considering enclosures for an external power supply and interface for this PC, as well as those super silent PC cases (google them) further isolating it from noise. Kicking around mini stillpoint risers for mother board, etc, but could get pricey. not sure how crazy i want to get but right now, leaning towards it. there are also "silent" power supplies and an assortment of stuff to build an ultra quiet puter. I am already using an ESI Juli@ and the only change I would make is to mod it.