Many routers allow multiple profiles for quickly changing accounts. However, each DSL line will only allow a single router connection and will not sync with multiple routers. You can use PPP passthrough on some routers, allowing you to "tunnel" via an existing connection to another ISP account. However, bear in mind that you are still limited to your line specification. So the two connections will contend (compete) for the available capacity of your line, it will not increase your download capacity. Passthrough is very useful but can make managing your home network very tricky. I would only recommend this for specific applications. A better solution might be to have a single ISP connection but use your router QoS to create multiple WiFI SSID's to manage the local traffic better. So some WiFi netowrks could be restricted to realtime services and heavily throttle or shape torrents and others may be less restricted. This way you can ensure that you predictably get the performance you need.