My current setup has a simple netgear switch between the cable modem (motorola) and wireless router (netgear).
I have 3 pc's plugged into the switch (each getting it's own ip) as well as the wireless router which hosts multiple pc's (4) & other devices (kindle, xbox, bluray player, mobile phone, etc.). This setup uses 4 ip's
An alternative setup would be to remove the switch, run the modem straight into the wireless router and wire the 3 wired pc's into the router. I'd only be using 1 ip in this case.
Other than the security benefits of putting everything behind the wireless router, should one or the other of these two setups work better from a performance standpoint? I thought originally that the multiple ip setup would work better, but now I'm wondering if having one device handle all traffic would actually be better.
Depends on what kind of traffic your putting through the cable modem. If you have a good router that does QOS and traffic shaping, you can fine tune things to uplink though the modem at an optimal rate. Other than that your putting all your traffic between two bottlenecks, rather than two links for only half your machines. If you have the IP's then its a waste not to use them. NAT has security benefits, but can be problematic for other services you might be running.
Are you hosting anything, or just generally surfing?