As far as expansion slots go for the ASRock P67 Pro3, there is one PCI Express x16, three PCI express x1, and three PCI slots. Lacking a second PCI Express x16 slot may rule out this motherboard for some, but for being a mid-range motherboard, this should not impair many users in that segment.
The P67 Pro3 motherboard socket supports second-generation "Sandy Bridge" Core i3 / i5 / i7 CPUs. This includes the K-series CPUs and those that support Hyper Threading and Intel Turbo Boost 2.0. This motherboard also boasts a V8 + 2 power phase design. The area around the CPU socket area is free of any obstructions, which should allow nearly any LGA-775/1155/1156 heatsink to be properly installed.
The I/O panel ports on this motherboard include two PS/2, six USB 2.0 ports, two USB 3.0 ports, one Gigabit Ethernet, one eSATA 3.0, and a mixture of audio connections. The audio codec is a Realtek ALC892 and a Realtek RTL8111E ASIC provides the Gigabit network connectivity. An Etron EJ168A ASIC provides two of the USB 3.0 ports.