If you want the CDs uncompressed, each 40 minute album will take up around 350MB – therefore 1,000 will need 350GB for the music.
Lets suppose you buy a 1TB drive and your photos are 5MB each – with 1,000 CDs on the drive, the drive will be full with 130,000 photos (which should be sufficient).
A 500GB drive would only allow for around 30,000 (5MB photos).
Other advice: if I downloaded 1,000 CDs and 5 years of photos to a dive (spent all that time doing it), I would buy a second drive as a backup, for when the inevitable happens.