Are all those devices connected wirelessly?
Do you have a TP-Link WR740N?
This router is limited to 150Mbps on the 2.4Ghz range for WLAN, and 10/100 on the LAN.
You're not going to find a consumer grade router that will keep up with the 1Gbps link, but a router upgrade to something that has dual band WLAN (2.4Ghz and 5Ghz) may help share the load on the wireless and make it feel "faster". This depends on whether or not your devices can connect to the 5Ghz WLAN.
Something with gigabit LAN would be nice, but since the WAN link on SOHO (small office/home office) devices is 10/100Mbps, it's not neccessary. This changes if you want to stream media between devices on the LAN/WLAN (not streaming from the internet)
Does the internet access feel slow? All devices slow? some devices slow?