The standard audio system in the Infiniti Q50 leaves a lot to be desired for a luxury branded sedan. In fact, the standard system is only a 6-speaker setup without Apple CarPlay or Android Auto. To get an upgraded sound system, you'd need to step up to the sport model and add a $7300 package to get the Bose setup which wouldn't be worthwhile for a lot of customers. Our customer went out and purchased his own compact powered subwoofer enclosure from MTX which we installed in the trunk to address the factory system's lack of bass.
This compact enclosure is on the weaker side (only 100W RMS) so power can be tapped simply from the fuse box. The 8" enclosure doesn't deliver deep bass but it does have a noticeable kick to it that's more satisfying than the factory system. We were able to get speaker level signal from the doors out of the B-pillar harness relatively easily. It's important to note that these cars have active noise cancellation and the speakers will sound terrible as soon as you start driving if you don't disable this feature. You can disable it by disconnecting the microphone for the active sound cancellation.
The amp has a remote bass knob which we installed on the driver's side just below the trunk release and traction control switch panel. We also did an 18% tint for the car to give it a more aggressive look and increased privacy for the kids in the back!