Found this website which helps you find out the best rates for you based on your connection.

http://scripting.elxdraco.net/calc.html

If you are not sure about your connection speed, use this website to find out:
http://www.speednet.com

When testing speed using the website, make sure you use the appropriate location. For example, i use Sdyney as my test server because most of the CS servers i play on are in Sydney.