Gaming Latency Help Please

Hello, I am currently having a problem with my wrt54g version 8.2 router. I've also tried a tp-link router which pretty much the same specs and still had this problem. When anyone in my house gets on the net while I am gaming on the ps3 or on a computer it lags me horribly to the point where I get frustrated and stop playing. This wouldn't be so bad except this means that I can really only get to play a game after midnight or 1am. My internet connection is currently 5m/756k which should be enough to run both an online game and facebook on my mother's computer. I tried setting up the mac address qos settings in dd-wrt and it had absolutely no affect at all on the situation. I may have done this wrong and if someone wants to teamview to help me set it up feel free. I'm just at my wit's end right now because nothing I do seems to work. 5m/756k is the best internet connection you can get around here btw.