MediaMonkey is used in some installations that have 2 Terabytes of music.
Performance depends on whether filters are used to segregate collections and
on how the database is configured.
See:
o Configure Database Performance / Robustness:
http://www.mediamonkey.com/support/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=75
o How to Improve Search Performance
http://www.mediamonkey.com/support/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=76