You don't say what the traffic consist of. Computer to computer transfers? or Internet slows down with 6 people using it at the same time. If it's the Internet, cheapest is to pay more for a faster connection.
It's a home connection, mostly youtube (although rarely all at the same time) and games
It shouldn't be a speed/bandwidth issue, we have a 28 megabit connection
Two of the computers sometimes get dropped from the internet