I used to have a similar issue. I had two roommates and between the three of us we had five computers and a smart phone running off one 8 Mbps cable connection. The internet connection was was routed out with a Linksys router and all computers were wired with the smart phone being wireless. We noticed that if even one of these devices was downloading something, latencies with gaming would increase significantly. I came up with the idea to use a old PC as a router. After doing this we found that we could download a number of things at once (even with bittorrent) and it had no noticeable impact on online gaming. I believe the problem was not due to bandwidth starvation, but due to the router not being able to switch between the various connections quickly enough. We used Coyote Linux, a floppy disk based Linux distro designed to transform older PCs into a router. All the older computer needs is a motherboard, CPU, RAM, a couple of network interface cards, and a floppy drive. You don't even need a keyboard or monitor. It functions just like any other home router in that it is configure through your web browser. Currently I am using pfSense, a router OS based on FreeBSD and it also works well and has many nice features but is more advanced and may be too complicated for someone without a fair bit of knowledge of networking concepts.