Best Data Source for Realtors and Investors

[Gerald Evans]

I am shopping for real estate tools to help grow my business, to include data sources for neighborhoods, phone numbers, email address, pre-foreclousure, etc. So far, Ive been referred to RedX, Landvoice, Espresso Agent and Deal Machine. Not sure if they all do the same thing. 

Any recommendations on which is the best for this type of data? 

Any others that I missed? 

Are any of them free or low cost?