Since you want to keep and use Apple device's here is my easy 2¢ worth.
1) Rip all your CDs into iTunes in ALAC. It is open source, lossless (future proof) and easily converted to (other lossless) FLAC, WAV or (lossy) AAC, MP3 formats.
2) A or B
A) Buy a used iPod classic and hook to your Onkyo as your music "server".
B) Buy an Airport Express and optical (SPDIF) cable then hook to your Onkyo and stream (lossless) direct from you Mac/PC's iTunes using your iPhone' Remote App (this is the method I use).
This is by far your easy way to future proof and manage your music at the highest quality while staying in the Apple music eccosystem.