Best contact management software?

I am a territory manager for the world’s largest enclosure manufacturer. I manage approximately 500 contacts that include distributors, contractors, consultants, and end user customers. What do YOU think is the best contact management software? I have use Outlook, ACT, Palm, and even created a very basic phone list in Excel. But I would like your opinions on what is best. I would prefer to work with something that has a notes field and that i can schedule reminders with. Thinking that ACT might be the best option. What do YOU think???