MSI MSI P67A-G45 (B3) Questions

[nofearskill]

Next week i am planning to build a pc on my own for the fist time, and i have few questions.
I am planning to get the MSI P67A-G45 (B3) + i5 2500k.

1. The motherboard has a 8-pin cpu power connecter. do i need to plug all 8 pins or just 4 of them? Note that i am not planning to do crazy overclocking. just 4.0GHz or even a little higher. im going to use the corsair h60 hydro cpu cooler.
- if i do need to plug all of them for 4.0 GHz, do i still need to plug 8 if i don't overclock at all?
- will the system fry or break faster if i plug all of them and not overclock at all?

2. I am also going to use one gtx 570, and as the motherboard supports sli, mabe in the future i will get another gtx 570, BUT iv saw many videos where they said that the second pci express will only work at 8x. what exactly dose that mean? will the performance get lower? not as high as it shod? is it worth it to get this motherboard for sli whit 8x or just get a non-sli motherboard?

thanks

 

[nofearskill]

sorry for the double topic. the page never loaded so i did it again

 

[Leaps-from-Shadows]

1. Always use the full 8-pin connection. If you don't, the system might not boot.

2. Most P67 boards revert to x8/x8 for SLI and CrossFire. This is normal. If you are using one monitor, then x8/x8 performs the same as x16/x16. It's only when you use huge multi-monitor resolutions like 5760x1200 that there is a small performance loss at x8/x8.