Assuming your cable modem has a router built-in and DHCP turned on, hook that and everything else into a switch. Location does not matter. Your equipment should find the router just fine and get their addresses from that. If you computer does not do this, then turn DHCP on in your computer. You can also save on running multiple cables to, say, your living room, by hooking a small switch to the one cable to your living room and hooking up a BR player/TV/media player, etc., to that second switch. Saves on running bunches of wires to one room in your house.
So far, in my house, I just upgraded to a 16 port switch in the basement and used the 8 port switch it replaced in the living room and have everything in the LR hooked into that. Works fine.
If you want to add wifi, you can buy a wireless access point and run ethernet to that. You do not need a wireless router if you have one already in your modem.