Joomla is a good cms so is several others. Please visit here and try a few and see which one meet your need : http://www.opensourcecms.com/. I will also recommend that becofe installing an extension make sure that you are installing them on the right platform, some of the extension's are for 1.0.12 while some only works on 1.5. If you can post what functions you are trying to use the extensions for I am sure some of us on this forum can direct you with the right extension to use. Good Luck.