Honestly, stop running Firefox, it's a total and complete piece of shit. And I'm surprised it's only trying to use 1.9GB of memory on your 2GB system and not 20GB.
Wow. Do your hate-ons usually give you problems with reading comprehension?
That's not Firefox using 1.9GB, that's total memory used, including the OS. My Mac Mini (quad core i7 w/4GB RAM, all of a month old) has:
Free: 967MB
Wired: 1.10GB
Active 1.42GB
Inactive: 640MB
Used: 3.05GB
My top RAM usage:
kernel_task (485MB)
Jenkins java client (267MB)
mds (254MB)
installd (99MB)
ruby (71MB -- this is a test harness for our build process)
Terminal (65MB)
loginwindow (58MB)
WindowServer (58MB)
storeagent (43MB)
Finder (35MB)
Python (31MB -- this is part of our build/test process)
Dock (30MB)
So dropping Terminal, and the stuff from our build processes, that's over 1GB just for the OS and services, before I start nickel and diming all the other little crap that's running (but taking less than 30MB each).
A freshly loaded Safari adds 70MB, FWIW. Since this Mini isn't intended as a desktop, I haven't bothered to install FF.