Well i dont know if it would make is noticable faster.. but if you have switches available put them in place of the #2 and #3 router. Then enable the wireless feature on the first router.
Or if you dont want to do that, just plug a single wireless capable router into either of the switches, and use for the wireless signals.
A switch is basically a router without all the ways of connection to an isp, and no firewalls. (which is ok cause your first one has it)