My way is the "cheap way"...
I drive my 4x4 with the mud-terrains for awhile.
Q45 suddenly gets a lot quieter.
But really, in general you may also want to inspect the rubber sealing not just around the top of the window, but also around the doors, and if you have one, the sunroof. Those will lose their resiliency over time and let that "loud" wind to seep between the cracks.