Many thanks for those useful links.
I am thinking to buy a Phenom II X 4 3.2Ghz (price 200$ in my country), being motivated by several posts here and would like to build something that I wont need to upgrade w/in next 2/3yrs. This is why, I think Ill need to employ the 450-500$ budget for the main system excluding the monitor.
And for your info I am not a hardcore gamer but I would try most of the popular games, so it has to have a moderate config.
If you have any suggestion, that is most welcome.