@Ogy,
Considering that sound, networking, firewire and everything else is built onto the motherboard, what more do you need? Video goes in the AGP slot.
I don't believe I've actually built a single computer in the last 5 years that needed more than one PCI slot and that was usually for a network card. (I have almost forgotten what a floppy drive looks like). I have zero PCI cards in my Pegasos and use it quite regularly.
Keep in mind that this is a Micro ATX motherboard and they normally NEVER come with more than three PCI slots (if they even have more than two).