Is the Intel Core 2 Duo E6600 faster than the Intel Dual E2180?

If you mean "better" in terms of performance, it is the Intel Core 2 Quad. The Core 2 Quad has 4 CPU cores, compared to the Core 2 Duo with only 2 CPU cores. This means that the Core 2 Quad is twice as fast as the Core 2 Duo and four times as fast as normal CPUs with only one core.

Well this answer is wrong to a great extent. the reason the e8500 is very popular still is because although it only has 2 cores each core is running at 3.16 GHz which makes it great for software or programs that only use 2 cores primarily. its great to have 4 cores but the q8200 only runs at 2.33 GHz. that means if your using something that only uses 2 core primarily the e8500 would be better because the 2 cores are 3.16GHz compared to the quads 2.33GHz. now for programs and softwares that are optimized to use 4 cores the quad core is obviouslt better because it will actually put the 3rd and 4th core to work. the reason i personally chose to get a e8500 is because its super easy to overclock and the truth is quad cores are not really being used yet. if you like doing video editing and a lot of multimedia work than the quad is probably for you but as far as playing games and doing simply everyday use the e8500 is definitely the way to go. the answer truly depends on what you like doing most. But from my personal opinion i would go with the e8500 because 4 cores are simply not that popular yet for programmers and it probably will be a couple of years before quad cores are really taken advantage of but when that time comes the quads of today will be cheap compared to the new ones that come out. so personally ill go for the e8500 but its all up to you