then just go through every option which is available in your bios and read up on each one... not only will this give you a better understanding of how your system works... but it will also give you suggestions as to what each setting works best at
i believe... spread spectrum varies the voltage to stablize it at stock speeds... but thats my understanding of spread spectrum for the cpu... could be the same for AGP... so for stock clocks id guess it would improve stability... but when the agp bus or the card itself is overclocked... i would guess that it would make stability and hopes of a good overclock vanish.
if you truly want to know... just do what i said before... search for Difinitive Bios Guide... i know for a fact it goes over agp spread spectrum
Spread spectrum refers to modulating the FSB (or AGP also in your case) signals so that electromagnetic interference is reduced. This is done in order for the motherboard to pass certain European compliance agency and FCC requirements.
What happens to the signals is that instead of all the signal power at the given frequency (and since it's a square wave odd harmonics close to the center frequency), a randomly generated "noise signal" is mixed in to literally "spread" the signal over a larger frequency range, thus reducing the power at given frequency.