Re: system monitor experiment
The "RAM used" figure in System Monitor refers only to the amount of RAM in active use. Any RAM over and above this will be used as cache, which does definitely speed things up as it avoids the whole "seek the hard disk to this position" bottleneck.
Ubuntu doesn't have a high active RAM requirement, which means it can use loads of cache if you want.
If you'd like to see how much cache is being used, then add the System Monitor applet to your Gnome panel and turn on the "Memory" indicator. The light green/cyan block is the cache, the pine green is the active RAM use.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.