All the PS Audio power cords have a removable ground pin for this very reason. They seem to be well thought out plugs.
In previous incarnations of my system, it worked well to have just the preamp with a 3-prong plug, and the other components (phono stage, power amp) on a 2-prong plug. Putting a 3-pong plug on my old power amp yielded a loud BUZZZ. However, my new monoblock amps (maybe due to their balanced input stage) and phono stage are both doing just fine with 3-prong plugs as well.
In previous incarnations of my system, it worked well to have just the preamp with a 3-prong plug, and the other components (phono stage, power amp) on a 2-prong plug. Putting a 3-pong plug on my old power amp yielded a loud BUZZZ. However, my new monoblock amps (maybe due to their balanced input stage) and phono stage are both doing just fine with 3-prong plugs as well.