One option would be to use an SME box as a router, and if you find the security's not strong enough (getting DOS'd etc), install a Juniper firewall in transparent bridged mode. That way you'd get the security benefits, but you wouldn't have to reconfigure anything, and you'd get SME's squid cache etc.
As cydonia said, most SOHO routers run linux or similar, and aren't hardware routers. Juniper/Cisco etc have firewall/routers that can route as fast as a switch, and provide a higher level of security. They're quite expensive though.