I was experiencing a bit of lag while playing DOA4, so did some research. What I found is this link that measures your actual travel time performance (instead of generic ping) utilizing Quake III type of traffic. This test demonstrates how their StreamEngine QoS technology works and what type of results you could get as a result. After a bit of further digging, found that the D-Link GamerLounge (DGL-4300) supports their technology (although it's called GameFuel). I picked one of these up about a week ago and I have to say that I'm very satisfied. With only making a single check box option enabled (GameFuel), everything seems to be working very smoothly. I will probably be adding the specific ports used by Xbox 360 with maximum priority at a later time to further test things. So if your interested in optimizing your upload bandwidth, you really should check this thing out.
Another interesting internet connection speed tester that I've used is at Speakeasy - Speed Test.