If you use domain name blocking you will have problems installing apps.
Without keyword filtering, it's a toss-up between whether you want to get update prompts or apps. Also, the exact URL will change with each version so it won't last.
Is DD-WRT supported for your router model? Check their router database:
(If you REALLY want the exact URL, enable DEBUG remote syslogs and pull it from the logs... that's how I got all the information I posted in my initial post. Keep in mind that it will change with the next release.)