Adding a second wireless router for more throughput?

Ok so I'm sure just like most people who regularly visit this site I have alot of devices in my house that use wifi. Off the top of my head: xbox, playstation, imac, ipad, iphones, apple tv's, slingbox, plus a bunch of other small devices that use wifi here and there. My questions is would it be better to add a second router just for the wireless devices that only use internet, and then keep the other wireless network for the devices that do need to talk to each other? and then have them both go to a switch then to my modem? Sometimes in our house we will be using the imac, xbox, phones on wifi, streaming to apple tv's etc all at the same time and i feel it slows down the home network for when i want to stream netflix to the main tv. I realize that my internet is only so fast, but i feel the internal network is the culprit. Any thoughts?