First of all, thank you for this good article. There are several texts on the Internet but mostly about products.
Now we have more than one option to watch over our network. There are also free and licensed tools to use for this purpose. However I am not hopeful about a magic box(or magic download) will solve monitoring problems.
This is why this article is a must read. I will also suggest to read http://cisco-network.com/hands-on/cisco-network-monitoring-common-mistakes/ for better understanding and to build a complete solution.