I'm thinking of getting a new cpu,and i'm looking out for the overclocking factor.

Should i go for the

Q6600 2.40 GHZ LGA775 - 1066 FSB
INTEL CORE 2 EXTREME QUAD CORE QX9650 3.00 GHZ LGA775 - 1333 FSB - BOX

Or one of the new 45 nm

E8400-E8500?

Which one do you suppose its better?

The E8400 will clock higher (About 600Mhz or so) and due to other Clock for Clock advantages it will do much better for processes that are not optimized for more than 2 cores. (Most Games make litte if any use of extra cores.)

If you do lots of stuff that is optimized for 4 cores (Most Encoding Video, etc..), then the Quad is the way to go.

So the e8400 will get approx. up to 3.6,the e8500?

Actually i do use lots of programms plus CAD applications,and need to play Crysis,bioshock and other games all the way.

The quad extreme edition how much could it reach via oc?

q6600 is base on 65nm, so the max out for everyday use is about 3.6GHZ, watercooling will push it higher.
q9650 is base on 45nm. I guess 4Ghz or so. Please remember good overclock needs more than just cpu. you have to pay close attention on psu, memory, motherboard and so on.

Well of course it depends on other parts and i'm not going to hold back,but i need a definite suggestion for what cpu should i go for.

is the e8500 worth the extra 80 euros?

Is the extreme edition quad worth all that money?

What is the main difference between 45nm and 65nm?

These are the questions that are troubling me so far.

1.no, E8XXX limit is about 4.0 to 4.5GHZ, E8500 has 9.5 multi and e*400 has 9
2. IF you will oc the cpu to the max, the answer will be no.
3. less voltage requirement and less heat.