Great list of all things Firefox
* Extensions * Search Engines * Themes * Customizing Firefox * More Firefox Resources

Worth a look.
Why bother getting extensions when Opera already has them all? Not even joking, the new 9 version has 95% of all those you just listed, including a much smarter password saver, popup blocker is much more intelligent, and auto form filler. Even has a built in "reader" you can highlight text and it will read it to you, and has voice recognicion, now includes widgets for anything it doesn't already have. Paired with a good skin from their website: Eg "The Blue Button v1.1", its great, oh yeah, and it has build in email client. And it's faster than firefox. Has everything and much more. I almost forgot. MOUSE GESTURES! You can do every function required just by holding the right click and moving the mouse in a certain direction. Back, forward, print, copy, new page, bookmarks, the list goes on and on. I could go on more many hours and provide at least 10 links showing why opera is faster/more efficient, than IE & FireFox, Safari, ect. Basically the fox gets trounced by it.
I didnt like DownTHEMall as it was kind of hanging on my PC (it was downloading the file but it I couldnt fined it in the download directory)

Ive downloaded the new opera and didnt like it. In my opinion Firefox is muchhhhhh better then browser available now
In no order in particular:

StumbleUpon - You can stumble on some really neat pages.
FasterFox - Faster, but not as fast as Opera. :-p
FlashGot - Download/link manager
Adblock - Blacks Ads...duh.
FoxyMeter - See how many pages you have surfed.
MouseGestures - Add the wonderful world of mouse gestures, my favorite feature ever, to firefox.
TimeTracker - Keeps track of how much time you spend on the net.
Ctrl Tab Preview - Works like Alt + Tab in windows, but now inside of firefox.
Colorful Tabs - Makes the browser look more alive.
Answers - Helps you keep on top of modern lingo.
I use Faviconize ( it makes my tabs smaller.