The Synology DS1621+ uses PCIe 3.0 x8 to open up 10GbE or 25GbE upgrades

The DS1621+ ships with four Gigabit Ethernet ports — solid but unremarkable. What makes it interesting is the PCIe 3.0 x8 slot inside, which is wide enough to run a 10GbE or even a 25GbE network card. Most NAS units cap their expansion slot at x4 or x2, so that x8 lane count gives you genuine headroom for future networking upgrades.