Hauling (junk hauling) would be the normal Search the List category to find well-rated and reviewed vendors to do this. Be sure to tell them if it is going to need some disassembly to get out of the building, as is likely if entertainment center is large.
Course, other alternative (for TV maybe only if working, though there are a lot of people who buy dead TV's for parts), would be something like Craiglist - though that means unknown people in your home, and probably higher risk of interior damage - dinged walls and scratch stairs and such.
