I configure these all the time with routers on ATM circuits.
But on a dsl line for example (2) 3 meg lines, you will never get one pc to download at 6 megs. This is because it would have to be aggregated in the EMBARQ redback router which is something they will not do. However, what you CAN do is load balance half of your users to use out one line and half out the other.
This would allow two users to download files at the same time at 3 meg each.