Well it is true that SATA ports do not like to much PCI speed. Now I have a Athlon64 3000+, Albatron K8X800 ProII , Radeon 9800, and using 2 SATA hard drives. I am running my FSB at 215. That puts the PCI at 35mhz and AGP 71mhz. BUT my onboard Envy sound, sata, ethernet, etc... are all running just fine. I have done encoding, hard gaming, etc... and my ststem is 100% stable.
NOW the newwer VIA chipset that should be out when the 939 chips come out is supposed to have a PCI and AGP lock.
From what I have heard the best overclcoking Athlon64 board is the Chaintech ZNF3-150 ZENITH which has a AGP lock, but no PCI lock.
But even then the breaking point seems to be around 220Mhz for most boards as NO Athlon64 board has PCI lock.