Verified answer

Intel Core i5 760 = 4 cores at 2.80Ghz

Intel Core2 Extreme 3.00GHz

Intel Core2 Quad 2.83Ghz

In my honest opinion the i5 would be much better, 4 cores, good clock speed, 8MB cache, hyper-threading technology, pretty sweet. Still depends on the price though.

Intel Core 2 Extreme X9650

If you want an answer, you'll have to name some specific processor models. This is too vague

If you are talking about the high end of each, it would be i5 - Core 2 Quad - Core 2 Extreme

EDIT: The 9650 is technically a Core 2 Quad also. i5 760 is better all around

Dual core i5? quad core i5? or sandy bridge i5?

EDIT:

i5 750 > core 2 extreme x9650 > core 2 quad Q9550

The core 2 extreme is a little bit better just because its running @ 3ghz and the i5 is @ 2.8. if the i5 was @ 3 it would be better.

The sandy bridge i5 are omgwtfbbq better then all of them lol. The i5-2500 beats the amd phenom II x6 1100T, and even some of the older i7s

intel Core i7 Extreme.

i5

Good question.