Linux is very efficient with ram. what app are you using to determine your ram usage? If you are using free, it is probably very acurate, but it shows all ram usage (including cached), and the actual amount of usage is usually much less.
try something like gnome-system-monitor. and you may be surprised to see you are "actively" using less than 300MB.
Example, here is what I show with free
total used free shared buffers cached
Mem: 515168 462392 52776 0 34852 182304
but gnome-system-monitor shows 243MB actively in use.