ps I swear you asked this question a few months back.
Anyway, here's what I recommend.
If you are computer savvy and like to build your own gear, you can try the DIY PC approach. There are some esoteric stuff available like Linear Power Supplies for PCs, small form factor motherboards with lower power CPUs that can remove the need for fans etc.
If you aren't and prefer an easier to buy solution, heres my recommendation: go to the Apple store online and custom order the middle Mac Mini with the following specs: 256GB SSD. If you want, you can opt for the upgraded 2.7GHz Quad Core CPU like I did. If you are comfortable opening up the Mini to upgrade the memory, order the 2x8GB memory for the 2012 Mini from OWC (macsales.com) and DIY. It's quite easy and a lot cheaper. If you don't feel comfortable, then pay Apple about 2.5x more to install it for you from the factory.
Once you get it, update the OS to the latest patches and use iTunes 11.
Buy and install Audirvana Plus beta (revision 11).
Depending on the size of your library, you may need to buy an external HDD. I recommend using a Seagate GoFlex which allows you to change the connection type to USB3 or FW800 or Thunderbolt. These interfaces are all perfectly functional and supported by the Mini and are in increasing order of price. The guideline is NOT to use the same connection interface as the path the audio is going to take. I'll cover them later.
Download XLD and use it to rip your CDs into AIFF. Theres an option in Preferences to add the files automatically to iTunes. iTunes can also rip the CDs for you, but XLD does better error correction and logging so you know if things have gone wrong. I have had a few discs that were not ripped properly (CD rot etc) and iTunes never told me they were dodgy. XLD will.
If you still have the budget, get the Berkeley Alpha USB device which takes USB from the computer and sends it to AES that your XDS1 can read. Remember when I said you shouldn't use the same interface for the audio and disk storage? Here's why. If you use the USB to send audio, you should not use USB HDD. Try to use the FW800 interface or the Thunderbolt option. With the Seagate GoFlex, you just swap the connector module to change that. The HDD data remains intact.
If you don't have the budget, get a mini Toslink to Toslink cable and use that to the XDS1.
ps I heard there's a new USB XDS1 coming end of the year. That could simplify the connection if your dealer has a trade in option
