Joomla and Mambo CMS have been developed by the same professionals of web design industry. So, they possess a lot of common features. For example similar code, system requirements, etc. At the same time new releases of Joomla will differ from Mambo. Having compared Joomla and Mambo CMS‘s you can notice that Joomla has more options, better security issues, regular updates, additional Built-in-Applications, etc.
With website templates you can get the best of both worlds. You can get something that is low-priced, was made by a professional developer, and is going to have at least a semi-professional look that should suit you just fine. These designs have been developed exclusively for professionals and individuals who want a simple solution. You will be able to add your own images, content, etc. to the site. As far as price goes though, it can definitely fluctuate. You can find low-priced templates or higher priced website templates.