WHS is so lightweight and requires such a small footprint that, while Chopper3's list is accurate, you're NEVER going to notice the differences between mobos with similar CPUs and memory. More than anything else, you'll notice external issues.
- Boot-up speed will depend on the speed of your drives and how much memory you have
- Backups will depend on how much bandwidth you have on your LAN (is it Gigabit?)
- Remote access will depend on your router (is it compatible?), your ISP (do they block ports?) and your upload speed (downloading to the laptop you brought on vacation).
I have a homebuilt WHS machine that used a low-end mobo, dual core AMD CPU and am very happy with it - except that, for some reason, if the system reboots (like from an update) and has an external USB hard drive, something in the BIOS hangs - doesn't matter if I have a USB DVD burner, that's ok, just a hard drive makes everything stop. So my requirement to have as many internal SATA ports as possible left me with plenty of space.
Next time, though, I'm going with a pre-packaged HP deal. Probably when the next version of WHS comes out.