6 People In 1 House Wireless Router Not Handling Traffic Well

I'm living in a house with 6 people on 2 floors, and the router isn't handling all the traffic well. I have an extra router that might be able to serve as an wireless access point, but from what I've been told that wouldn't solve anything if the problem was that the first router doesn't have the capacity for that much traffic. It's a 50+ dollar wireless N router though and fairly new (forgot the model number)