You can find out the pages that the se's have indexed by putting this in the search box: site:
www.powerlife-solutions.com
As you can see by the below, Google has already indexed 33 of your pages:
http://www.google.com/search?hl=en&l...om&btnG=Search
An add-on domain has it's own domain name which you must purchase. A sub-domain is simply part of the same domain name.
It really depends on what you want to do with the mini-sites. I really think you'd probably be better off working with making ONE site the best it can be and add pages to it to help it get better - unless the mini sites have reasons to be separate. And if they do, then they probably would be better off as add-on domains.