Looking for a flexible CRM suited to nonprofit membership organizations

My employer is currently looking at CRMs to act as a membership database for our organization. We are a non-profit, membership organization. I am most familiar with CiviCRM and although I like that it is geared towards non-profits and not sales organizations, I'm not sure if it is the best choice for us in terms of other functionality.

Some of the key features we're looking for:

• The ability to generate a report of incomplete or out-of-date fields for contacts so we can solicit focused updates from contacts
• The ability to represent arbitrary entities (i.e. not just individuals and organizations) and have these linked to individuals or organizations
• Ability to track event participation
• Native support or API hooks that would link database contacts to Drupal users and let us record activities like commenting on block posts or sharing links to our content.

If anyone has any experience with particular CRMs implementing some of this functionality, I would love to hear your experiences.

Best,
Geoff