By rights you should have a single modem to your isp, then connect your stand alone router to that, then for extra wifi coverage to other area's in your home you can bridge spare routers to act as repeaters and place them where they'll do the most good. There are many how to's on the web for doing this. There shouldn't be any limit to how many repeater routers you can have. Do note though that a repeater's wifi signals will be halved vs a full on access point. You should be able to find more info on doing this on SmallNetBuilder
You see there is only one constant. One universal. It is the only real truth. Causality. Action, reaction. Cause and effect.