Hi. I'm another member who's going to recommend the Raspberry Pi, and add my vote for the Durio Sound version, which I liked more than the £5k Classe CDP I was using at the time. I burned my CD collection to disc, sold the CDP, and have never looked back.
Here's what you'd need if you decide to try this. Durio Sound Dual Mono All-the-way- Assembled
http://www.gravitech.us/duduala.html. This comes with all the hardware needed except the HDD and power supply.
It has the benefit of an on-board switching power supply so you can power it three different ways. Either USB power to the RPi direct (not recommended), or DC wall wart (Maplins here, or Radio Shack in the US) or AC transformer to the Durio Pro board. I use this
http://www.ebay.co.uk/itm/272263526102? ... EBIDX%3AIT.
I made up my own cable for the power supply using this
http://www.ebay.co.uk/itm/380335424755? ... EBIDX%3AIT and this
http://www.ebay.co.uk/itm/231704839431? ... EBIDX%3AIT.
At $185 it's an absolute steal, although I can't say whether it's any better or worse than any of the other I2s DAC's that are being recommended here. One plus is that it's as near to plug and play as you're likely to get in this sector of the market, and there's always plenty of help available here to get it up and running.
As for why it's better than a normal computer? The pi B+ upwards has a dedicated audio (I2S) bus, and it has no other tasks interrupting it with requests for the CPU etc. It is a proper, stand alone, dedicated music server, no whirring fans, and can be controlled from any device on your home network that can run a browser. I use a tablet or my laptop.
The only drawback for me is the lack of a suitable case for it, so if you have kids or pets it's a little bit vulnerable to damage.
Bi-amped A80's, P90sa, LS6, AP10h, Phono2/2 PSU's, BMU, SSC, SSP2, Raspberry pi/Durio Sound Dacs, Rega RP6/Dynavector 10x5, Royd RR2.