I lost track of the number of actual CDs, however...
Music Match says we have:
8406 items with a total playing time of 601 hours ( 25 days) taking up 38.67 GB of space.
iTunes says we have:
8558 items with a total playing time of 33.1 days (794 hours) taking up 41.1 GB of space.
Difference is a few AAC files I've aquired over time and lots of Audible* content.
***Edit: Add link to Audible.
I've had a Susie Bright Audible show subscription for over 2 years and have downloaded 30+ books. Many have been converted to MP3, so there is duplication in time and item count.