Get rid of Avast... and McAfee? why do you have two antivirus programs? use Microsoft Security Essentials and your brain.
As for those Firefox extensions, consider disabling DownThemAll until you're sure you're going to download a lot of stuff, or use it in a different Firefox profile and run it via shortcut with:
at the end, the latter allows you to run two instances of FF at once if you must download with DownThemAll while surfing with your usual profile.
Make sure the Greasemonkey scripts you run aren't bloated, run less of them, or just disable Greasemonkey.
I stopped using NoScript since its creator went and tried to meddle with another extension, to replace it I used RequestPolicy
and haven't looked back.
Though you didn't show an image of the Plugins you have, the only one I have enabled is Flash.
Lastly, if you want an optimized version of Firefox, try Palemoon
. It's a tweaked build of Firefox that should help with performance issues on some level.