Define better performance.
While being a direct replacement for the NGK CR8EH-9, the Iridium tipped NGK CR8EHIX-9 may provide slightly different combustion characteristics which can slightly alter the "feel" of the motor, but doesn't necessarily make it a better performance plug. In fact the spark plug has little affect on performance unless it more closely matches the requirements of the engine as regards heat range, tip protrusion, or fouling resistance.
One huge advantage to the Iridium plug is longevity -- the precious metal electrode tips do not erode as the plain steel ones do, so it will maintain the recommended gap for practically the life of the engine. Now that's performance!
In general, when you see a company advertising plugs that they claim will noticably improve horsepower or mileage they fall under the heading of snake oil remedies and conversion kits to run your car on water. There are no large gains to be had from such things unless your plugs are so old they barely light the fires.
By the way, the Iridium plugs are generally available online for only about 50 cents to a dollar per plug more than the conventional ones, so there is little incentive to stick with the conventional plugs.
If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
------- Rob --------