I know of one but it costs so it probably wouldn't be much help. See
http://www.broadbandreports.com/tools (some of these tests are free.)
About USB modems see this page & scroll down to
3.4 USB-based modems/routers Where high demand net apps such as games, p2p & video conferencing can suffer.
By the way do you use the Resume button on all your incomplete files after you open LW? This have side-FX. It can affect LW's connection quality, use up all of LW's resources & your computers & can steal all of your bandwidth. It puts a lot of stress on all of the above.