Take a Stinger 2.0T Premium out, then take the Optima SXL, drive them on he same stretch of road and keep track of the noise level at varying speeds and see how they compare. After driving the Stinger Premium and then getting back into my Optima Hybrid EX and drove it on the same road, the Stinger was louder at 55 mph in the cabin than the Optima at 70. I drove the GT and the Premium back to back previously and noted that the cabin was louder, we went to Audi to compare it to an A5 Sportback, the noise level in the Audi seemed quieter but there was some noise as well that made it not as quiet as the GT. Now, I didn't drive those cars on the highway but since they sounded louder than my Optima, I figured they would be more noise at highway speeds. We plan to go back to Audi to do a longer drive in the A5 as well as do a longer drive in the Stinger Premium and get some highway time in to really compare. I know different road type and tires can make for a noisier cabin.
By the way, what car do you currently drive?