Before you go spending your money, what are you going to be using the computer for, and if it's gaming what games?
Also you say about buying a new monitor, what size?
The reason I ask is that in general gaming at the resolution of your current monitor you will not see any significant improvement if you were to upgrade your existing processor and graphics card. Unless you are interested in benchmark results your current processor especially will be fine as very few games will currently take advantage of a quad core processor. Also your graphics card is capable of playing pretty much any current game at high settings at your monitors native resolution. Unless you are considering buying a montor with a screen size of 24" or bigger the differences will be hardly noticable (except Crysis but then very few cards if any can play that without struggling
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