Whatever router you get your bandwidth (download speed) will still be shared out between the devices attached to it. ie: if you download at 5Mbps and 2 pcs are downloading at the same time they have to share the 5Mbps (not an equal share - it depends on what each pc is doing) Also if you use wireless that is a slower speed than the speed from router via a cable to pc/laptop.
However if you have a very old router it might be time to get a new one. Have you done any download speed tests? http://www.speedtest.net/ is a good one to use.