I believe I can help you, dear man!
I have the same motherboard as you, ya see. First off, ensure you have the most upto date BIOS (download from the gigabyte website)
BE WARNED THOUGH: when I updated my BIOS it wiped my RAID 0 sata array. could have just been me being a bit of a foo. if you've just got the single hdd there should be no problems.
Step 2: in the BIOS when you increase the FSB reduce the HT multiplier to 2.5. don't ask me why, it's just that this is the highest multiplier the board will like for some reason. Leave the K8 multiplier on auto. whack the FSB up to 160, stick a bit more voltage through, and DON'T FORGET THIS STEP: you must increase the HT voltage to the maximum allowed, this setting is right at the bottom of the overclocking menu.
I found this all out for myself (took a while) I hope it works for you too.
Using this motherboard I can have my 3700 san diego at 3ghz (albeit unstable 😀) however I have found that the board doesnt supply the voltage that it states in the BIOS, mine was slightly lower. And even at max volts (1.75v) I can't get my 3Ghz stable.