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I know..About ten minutes ago I saw that the FSB is 800Mhz..I guess I will have to buy a new mobo,case,proccesor

..Thats OK..So quads are better in general..
Not necassarily. The jump from single to core is noticeable for most users, ie encoding music at 95% CPU load whilst browsing internet, so you still have one core free. On a quad it'll either be quicker (if you set higher priority) or less CPU usage across the board.
Only if the applications support it, and you're doing lots of heavy CPU processes. I think currently it's better to go for a faster dual core, then a slower quad core if gaming is prime computer usage.
Since this forum is about FS, then for the quad to be worthwhile purchase, you'll want it to use all four cores. Once a app is multi-threaded it should work on dual, quad, eight core etc....but if it's only using 10% on each core on a quad it's not making full use of it.
A bit like the hype with Crysis using quads. It doesn't.