Put the DSL modemrouter in "bridge" mode, so it is only a "dumb" modem, and run pfSense on some older HW. Or use your wireless router or another high end router. Most things you can buy are better than the stuff your ISP gives you. I have an Atom powered pfSense box and it works great with heavy traffic on 30/30 + 12/1 line. Never any trouble. But the Thompson that came with one of the clients could not even handle me seeding Ubuntu...