How best to handle a lot of peer-to-peer traffic?

I have an 15Mbit cable internet connect shared between 4 people. Two of the connections are wired and the rest of the connections are wireless. Everyone uses torrents. This of course makes playing online games and streaming video very inconsistent. It is sometimes possible to tell everyone to shutdown their torrents, but it is a hassle. The problem I've been told here is not a bandwidth issue but an issue with the router not being able to handle (forgive me if I use the incorrect terminology) the amount of connections/requests/traffic its been asked to process (generated almost exclusively from torrents). Its inability to keep up is what causing the poor performance in latency sensitive programs.

The current setup we have is Cable Modem -> Router -> Computers

I've been told that I need a router that can process more traffic effectively or to put a computer between the cable modem and router. Putting a computer between the cable modem and router would probably be the easiest solution since I have a media server that I would assume could fill both positions simutaneously. Of course all would be for not if everyone continued to use torrents on their PCs, which is why the Media/Router PC would be setup so everyone would remotely queue their torrents on that PC. If its relevant, the Media PC is a Phenom 9500 on Vista. The other PCs in the house would have XP or Vista.

The proposed setup would be Cable Modem -> Media/Router PC -> Router -> Other computers.

Now, I think I've covered most of my bases, I just want to see anyone can point out any problems with what I think should work or alternative solutions to reducing/elimating "high pings/lag spikes" while allowing everyone to continue using torrents freely.