Then you only need one extension, that is search with http://searchwith.mozdev.org/
What to do for the other extensions - highlight them and then search with "search with" to find the others.
The mozdev.org site also has a large collection of add-ons/extensions, also those temporarily in the sandbox.
Mind this, it is advisable to scan your extensions before downloading them, and download them preferably from the https site so you know you get the real mac coy.
Then some extensions may interfere with other extensions. Some extensions have known memory leaks,
error console console2 is better than the default error console that comes with FF or Flock, locationbar2 is better than the default address bar that comes with FF or Flock. Why the developers did not gave up their inferior versions is beyond me. Also why NoScript for security reasons was not brought in by default, but then as you come to think of it; commercialists rather incorporate Stumble upon and Alexa's as default then NoScript or Stealther. Those that earn from ad-crap vote those extensions out that hinder them too much in getting money for your clickstream, like an extension like RDR that make your browser definitely safer, see: http://redirectremover.mozdev.org/
Every security aware user of this forum knows the insecurity of certain things in the browser, like: redirects, certain tracking third party cookies, malicious script vectors, silent downloads etc. But more secure browsers has not reached the big masses yet.