Check right over the bottom pci slot to find out what rev board that you have. If it is a rev 1.02 then you won't have agp/pci locks. There was a early bios that would lock the pci bus but it won't work with a Winchester. If you have a rev 2 board then you will have locks. Just set the AGP/PCI to 66/33. There are some people that claim the via sata ports lack locks, even if pci is locked. However, I have a rev 2 and have had the HTT up to 250 with sata hdd's. So the via sata ports on mine are definitely locked.
The MSI Neo2 has locks on two of the sata ports (ones by the AGP slot) and is considered the best OC board with AGP. It would suit your purposes well.