Just to clarify things here a bit, solid engine mounts will not increase your power or torque to the wheels, all they do is keep the drivetrain from bouncing around turing large changes in drivetrain torque output.
Average people, even those who drive fairly agressively on the street, are usually not good candidates for solid engine mounts... the increase in NVH (Noise Vibration and Harshness) is very noticeable, while improvements in drivetrain responsiveness are often not (especially with an automatic transmission).
If you're having problems with wheel hop or are driving your (manual transmission) car regularly on a road course, then stiffening the engine mounts can be worthwhile. Other than that, improvements are often debatable. NVH is guaranteed to increase over stock levels.
I'm not poo-pooing solid mounts (they definitely have their place), I'm just trying to clarify why you should or shouldn't buy them. There seemed to be an "air" of suggesting that these would increase power and torque at the wheels, which is not true.
Correct, these will not increase engine flywheel torque; what it will allow you to do is more efficiently transfer that engine torque to the wheels.
Meaning in real world road conditions you will have more torque to the wheels (due to better transfer efficiency), rather than loosing it through the drivetrain “flopping around.” The engine flopping/moving around takes torque, which these will not allow this movement.
They also reduce wheel hop if present.
They also offer you to "feel" how the car is reacting/feeling, to know how hard you are pushing the vehicle. (Better responce)
Good reference sites are Energy Suspension or Prothane. They do not make products for the Cruze, but have good information on what poly/solid mounts offer; which in re cap has been stated above by us.