Depends on which inserts you get. The Energy Suspension inserts come in a pack of 3 (front tranny / A/C mount / rear tortion mount). They are not all that stiff and will cause a little more body vibration, but it's not all that bad. If you want to experience some crazy vibration, also get the Protane kit. This kit comes with inserts for the rear tortion / cam mount / upper tranny mount and these are pretty solid.

Furthermore, if you don't like listening to CDs, get the J's Racing front tranny / A/C mount replacement mounts. Those things are CRAZY stiff.