You do not have to convert the CDs to AIFFs or WAVs, et cetera. High quality MP3s will suffice ... just make sure you use a high compression rate ( exempli gratia: 224 Bit Rate, with VBR ).
HoloSync will only fail if you are using their proprietary higher levels ( Awakening Level 1 and above ). I remaster audio tracks and am on HoloSync Awakening Level 4 ... and have done research on this.
I hope this helps.