Old iMac using iTunes as the library/server. Rip CDs into old iMac using XLD which is a free app for ripping CDs. BitPerfect is a cheap app that can run using iTunes but bypassing all other interference from iTunes. Get a good quality USB cable to run from your computer to your DAC.
That's all you'd need. You can run it all remotely using your smart phone via Apple Remote. If you are concerned about SQ issues with iTunes there are a number of relatively cheap apps like JRiver that can be used in its place and supposedly sound better.