Explicitly disabling WPS in DD-WRT is unnecessary because DD-WRT doesn’t implement WPS at all–which is a good thing. There’s no setting to look for, it’s just automatic.
Linksys routers are known to have a setting to disable WPS, but I’ve read several accounts stating the setting doesn’t actually do anything–WPS stays enabled. So loading aftermarket firmware is the best fix available.
DD-WRT also gives you some other good features, like creating VLANs. Want your web server on a different VLAN? You can do that. Want your wireless clients on a different VLAN, to protect the rest of your network in case a warwalker or wardriver manages to get in? You can do that.
VLANs are an option as long as your router has a Broadcom chipset in it, which all Linksys routers do.
What’s a VLAN? Splitting a switch into multiple networks for improved security and (sometimes) performance. Enterprise switches do that; DD-WRT lets you bring that capability to your home network too.