5.8 GHz is just a channel in the 5 GHz range. The FiOS Quantum Router or any other dual band router has a range of channel 36 to 165. For example channel 36 is 5170-5190 and channel 165 is 5815-5835. If you want you FiOS router to work specifically at 5.8 Ghz then login and change the channel from automatic to channel 165. The mini clients also don't have to be connected wireless. You can connect them with coax.