Slow Download Speeds

I share a home network with my parents but recently we have noticed that when I am downloading something that both of their internet's slow down. Mom is on a desktop and dad is on a laptop. We are using a DSL connection and normally download at the speed of about 450-600kb/s. We installed a new router recently but did not notice anything then. My mom then started to complain that her internet was running slow. During that time I was downloading, and when I stopped the download her internet sped up. Same goes with my dad who also complained about a slow connection on the wireless which stopped when I halted my download. To try and fix the problem I also tried to install a switch but that did not seem to work either. Does anyone have any suggestions as to what I should do?

EDIT: P.S. It is a Actiontec GT724WGR.

All right thanks for the reply...I was getting similar responses from people on other forums. This really sucks until February when we get Fiber Optics, in the meantime I am stuck with DSL.

hmmm...I have a 100mbps connection as well, though I never seem to get past 12000k on speedtest...so it looks normal to me, although a low of 5000k mbps is a bit on the low side...

Is your connection speed jumping around, or is it more or less constant at any particualr point in time? It could be a bad connection somewhere down the line (my underground cables cause my connection to go bonkers when it rains, for instance...).

Spre not Mbps but Kbps