What's the most ideal frequency ratio between the CPU and RAM? What kind of theory is this based on(if you know)? In addition, does a 3GHz dual core CPU give better performance than a 2.66GHz quad core one in most case? Lastly, how do you choose motherboard? (e.g. Would you choose ASUS P5Q-E or ASUS P5KPL? why? ) Thanks a lot!
2) I'm guessing you're comparing the Q94xx to the e8400, the e8400 wins because it has a higher Instruction rate in current software as it can only use one or two cores, however if you use an app which can use 3+ cores the quad core will pull ahead of the dual core.
3) go for the motherboard which has the right features for your needs and has a P4x or X48 chipset. So if you're an overclocker or you plan on using multiple cards you would go for the X48 series motherboard as they have 32 PCIe lanes and when not all of those are in use the chipset can run at a lower temp allowing higher overclocks.
1)for the i7 there is no best ratio, for core 2 and below the best is 1:1
2) the e8400 and i7 920 should be pretty even in todays apps because the i7 has a higher IPC, but the i7 will win in apps which use more than 2 threads,and the Q9550 will be in between the two in those apps but below both in <2 threaded apps.
3) the i7 doesn't work in either of those boards as it uses the 1366 socket where motherboards are a good deal more expensive. but for the core 2 line, the P5Q-E is a far better choice.