I am working with a friend on building a web site, in general this web site will be a custom web app along with a very custom social network type of thing..

Currently I have a mock-up site that uses simple PHP with AJAX and JSON and JQUERY and I love how it works, I love the way it all fits together.
But for a mock-up I did not implement any of the Social Network design patterns such as a login, rating, groups etc.. 
This brought me to a higher level of decision making requirement, I need to decide if I want to develop all this functionality by hand or use some kind of a framework.

I spent this entire day researching, and it would seem that using Drupal and such frameworks will make the Social Network part easy (overlooking the customization requirement for now..) but will make client side Web App development less so.

I found some other frameworks that are more developer friendly (customizable) such as Zend and Symfony etc.. **but** these seem to take allot of the power from the client and implement it in the server side, to me this seems a waste (and an unjustified performance bottleneck) ..

Finally I found Aptana Jaxer framework that seems to think the same way I feel.
That said it seems a bit under-developed, I didn't find modules for a social network and the community around it seems thin.. (searching Jaxer in StackOverflow returns few results)
So other then making server side DB comm a bit simpler it does not help me greatly.. 

My requirements are a good facility to develop web apps on while containing all the user centric logic usually used for social networks in advance.

**What would you recommend?**

EDIT:
OK, lats fine tune this question, after considering this abit further, is there a good down loadable source of a social network site in PHP that I can work around in building my web app? (I really like using JQUERY AJAX JSON etc..)