We wrote a nice review whether you should buy Dual Core Processor now. One of the reader Anonymous posted:-
Iam buying a new computer shud i buy Intel or AMD dual core ?
What's a single core ?
Well single core is nothing but the single processors that is available in the market, dual core is nothing but 2 processors. Single the launch of Dual core, single core processors cost are falling like shooting stars and is the best time to buy them !
So I would suggest you go for a good configuration Single core is a good buy ! and Don't be stingy with RAM !!!!
AMD 3200+ is a great option for a average desktop computer and so is 2.8 Ghz Celeron.