i have a d975bx2 and i would like to oc a q6700 on this what is the limit of the 975x chipset and the q6700?

Depends on how high you can get the front side bus.
1066 FSB = 2.66GHz
1333 FSB= 3.33GHz

I heard someone say they got their 965 chipset up to 1600FSB.
If thats the case you can get it as high as 4.0GHz.  
Depend on your Mobo. Might not be able to overclock that mobo

The 975X chipset in general is not a good overclocker, and you tend to need to pump voltage through it to be able to get a decent overclock. That said, 333MHz is likely to be attainable, but even that may not be possible depending on what voltage adjustments to CPU and NB voltage your board supports. The most I ever pushed on my old 975X board was 280 without being able to raise the voltage on the northbridge, using my E4400.

I can overclock my E6600 in my MSI 975X Platinum to 333MHz. Then again I only have DDR2 667 RAM.

so will it be a challenge to get it to 3.0 on this.  
 
why is the q6600 more popular than the q6700 will that change because of the new price for the q6700.    

Most likely, the Q6700 used to be a huge price increase for very little actual bonus. 3GHz may be attainable, but I have no experience about how 975X overclocks quadcores, only how it clocks duals.

doesn't the 6700 oc easier  
what are the advantages of the q6700?
what kind of cooling would i need for 3.0, 3.6, 4.0-with a new mobo?

http://www.frostytech.com/top5heat [...] ELHEATSINK

will i be lucky to hit 3.4 with it even with liquid cooling (which i would get if i could go higher)