You are actually looking for a wireless access point rather than a range extender. This means that just about any router will do the job, but if you want dual band it will be a bit more expensive. I would think you would want one which is capable of simultaneous dual band which means it can operate on both bands at the same time. Selectable dual band can only operate on one band at a time. This one from TP is something like what you want. TP-Link TL-WDR4300 Simultaneous Dual-Band N750 Wireless-N Broadband Router (750Mbps)