Use Multiple Wireless Access Points to Extend Range
Typically, vendors such as Linksys charge more for devices which work as standalone WAPs because routers are typically used by home users and WAPs are more popular for businesses. With DD-WRT you can buy a device marketed as a router and use it as a WAP.
If you are installing additional Access Points to cover a broader area with Wi-Fi access, it is possible to allow clients to roam freely between them. The common method is to use the same SSID and Security settings on each access point.
Use a different channel on each AP. e.g. if you are in the US and installed two access points, use channels #1 and #11. Or if three access points, then use channels #1, #6, and #11 (setting the channels at least 5 apart should help keep interference between APs to a minimum). If you have a residential gateway with wireless turned on, and just one AP, then the same applies: each gets a different channel.
When using multiple Access Points, each one should be wired to the LAN. They can even be attached to different switches within the same organization.