This is pretty common. Wireless G is limited to 20Mbps up or down, or 10Mbps with both directions being used at the same time. Honestly, I would personally say keep your current FiOS router but set up an access point for Wireless access which supports 802.11n. Any ordinary router can be repurposed as an access point, and many units in the $80 range support dual band and higher speeds than the current FiOS routers do.
The trick to the access points are to disable the FiOS router's wireless and to wire up your access point to the FiOS router. If you already have a Rev. F ActionTec router or newer, moving the router to use WPA2 security, and a wireless mode supporting Wireless N will help with your speeds wirelessly.