It's actually a range extender, so it duplicates your router's packets and cuts throughput in half. It would work with routers that support 802.11n, and to get the most out of it, you'd use a router with 2x2:2 802.11n to match the extender's 300 Mbps link rate.
Not sure why they call it an amplifier, which would amplify the signal coming from a router's radio chain while connected to the radio chain with pigtail cables.