In your case, the expansion slots can probably be disregarded. I like to keep my options open for the boards I buy as I like the option of redploying in a different use case. For example, if you ever got the crazy notion of adding 1 or 2 Ceton InfiniTV cards, a GPU, a second NIC, SATA card, etc. it would be more difficult or impossible with only two free PCIe slots.
