Hello
My personal opinion is that Satellite L20 is not designed for heavy operations and it is definitely not gaming machine. If you compare price for Satellite A and Satellite L notebooks you will understand why. I am pretty sure this notebook is designed for Internet, Office and all simple “every day” activities.
RAM upgrade is very good and I am sure it helps a lot but CPU upgrade is not the solution. CPU upgrade is not supported. You must also understand that every hardware platform is designed for optimal hardware activity. CPU, graphics, cooling system and other hardware components must work harmonic and without overheating. Stronger CPU means more heat.
In my opinion you should optimize preinstalled operating system in hope software you use will runs better and more stabile.
Bu the way:
http://aps2.toshiba-tro.de/kb0/TSB9401AX0001R01.htm