At 1.28 mbps you should be able to watch U-tube videos if nothing else is downloading at the same time. You're pretty much out of luck with those speeds for Netflix, Amazon, etc.
What speed has AT&T said you should be getting? What browser are you using, and do you have multiple tabs open?
Use Networx and find out what programs are downloading stuff, that will give you an idea of what you need to shut down when you want decent speeds, working with what you have. You can set Networx to list the software and how much bandwidth they are using.
Disabling add-ons might not do you much good if you simply don't have the bandwidth to begin with.