I use three of them..
In purpose for Check RAM and CPU usage, I use Process Explorer because I am more comfortable with its interface.
In purpose for Check which Process that consume bandwith, I use Process Hacker (because Process Explorer don't list Network Activity). This tool can Solve your Bandwith Problem.
In purpose for decide Which Service can be set to Disable or Manual, I use System Explorer. The Service Tab of System Explorer is most powerfull since it can Hide Microsoft Services, See Startup Type of each Service (Auto or Demand), See which Service is Started or Stopped.
Moreover, System Explorer has History tab to Record and Display Process activity.