Well considering you picked the latest draft n router to be supported by DD-WRT I would go for it. Only downside for this router is no dual band 2.4 ghz and 5 ghz support as well as no gigabit ethernet. Keep in mind your throughput is going to take a huge hit for using any other encryption besides WPA2 with a draft n card.
Nope DD-WRT is an alternative firmware that you can flash on to certain routers mostly linksys and buffalo. It got it's name from the WRT-54 series linksys routers which where the first it worked on. It's does void your warranty but the features are worth it. Just google DD-WRT and check if your router is compatible if your interested.