Website Design: Best Option for my new site?

I am looking to build basically a social network for small businesses. I need to figure out what languages/technologies I should use to accomplish this. I currently have a "test" site up and running and it uses Joomla! CMS 1.5. My page currently uses, HTML, CSS, PHP, JavaScript, XML, MySQL and HTTP technologies. I want my new page to automatically display the page that is relevant to the users zip code based on their IP address. Should I use Joomla or something else? Am i pointed in the right direction. This site is going to be nationwide in the United States and would list over 26 million businesses in the United States as of 2011. If anybody has any thoughts questions or help I would be greatly appreciative. THANKS IN ADVANCE!!

What an interesting place and Fantastic question i appreciate on this and looking for

I think that you might need to look into hiring a developer, especially if you are creating a social network to go nationwide.

Security is key - you need a stable back-end to ensure that business /personal information is kept secure.

Joomla is the best option to handle and maintain your website easily...

Joomla is best for website designing, there are many free and premium Joomla templates available on internet which are used by designers to design website, and it makes their work easy