How can I choose the best CPU?

Ok I have read up on the difference between the Dual core vs Dual core duo or dual core 2 duo and I find very little difference and I do not care to open a old can of worms....

to keep this simple I have a Socket LGA775 motherboard

So my real question is which one is the biggest bang for the buck...

ie. if I buy a E6300 @ 1.86GHz 1066FSB 2x1MB L2 Cache ($46)

will it be better or worse than a E4300 1.8Ghz 800MHZ BUS 2MB Cache($53)

or will I get a better deal with a E5200 2.5GHz 2MB cache 800MHz ($47)

I am willing to pay ($65) for CPU but I can not tell if it would pay to

put in a faster FSB or a faster clock speed like the E5200 2.5GHz


PS the MOBO =
MSI G41M-P26 Socket 775 Motherboard; Core 2 Quad Intel G41 DDR3

No over clocking for me... Intel only...