Router != bridge.
A bridge is a relatively dumb network device that connects different network types (Ethernet to wireless, phoneline to Ethernet, token ring to foo, etc.) A router is a more "intelligent" device that directs network traffic to an appropriate location. (In the case of "home routers" like the Linksys, they're basically NAT-in-a-box, but commercial grade Cisco, Cabletron, etc. routers do much more.)
If you're looking at a device advertised as a bridge, it probably doesn't have routing functionality built in. Any router/broadband gateway that lists support for HomePNA (or 802.11b for wireless) is a router with a built-in bridge.
Typically you will pay more for the router if it includes this bridge but still pay less overall than if you bought the bridge separate from the router. This is not to say you wouldn't want to do that, however -- I did not and do not like Linksys's 802.11b feature set, so I have a plain jane Linksys BEFSR11 for the router and a D-Link DWL-1000AP for the wireless access point.