I have been pushing my office to switch to an all Mac network, but they are moving forward cautiously. We are buying (4) used iMacs for a select group of assistants to use as a pilot study of integrating OSX into our work flow; however, the IT staff is concerned about their ability to sufficiently test the hardware before purchasing used Macs. For budgetary reasons we are not going to buy refurbished iMacs. Does anyone know of utility software that can be run on OSX to diagnose hardware? The software should be able to run tests on all system hardware (i.e. video, hard disk, CPU, etc.) and report out results. Ideally it would be open source, but all recommendations are appreciated. TIA!