Between your PC and any server you are looking at, lies miles (hundreds, thousands even) of cable. Any noise on any section of cable with affect the speed. Plus theres also the contention ratio (thats the number of people using the same service as you at the same time) to content with.
NO software will give your 56k modem broadband speeds.
If you want to try anything try free software like CyberTweak click here Its free and no guarentees...