HD's will die when overclocking because the PCI bus frequency gets raised. That's why it's best not to break 37mhz on your PCI bus (if your bios has the option to lock your agp/pci bus, use it!).

As for the mainboard, I'd suggest ya go with the SiS655 mainboards if you want to buy right now... if not, wait a few weeks and get an i875P chipset motherboard. Gigabyte has a nice SiS655 mainboard, but as for the i875P boards... can't make any recommendations until I get me hands on one of those :D