Hey guys. I've had the UR Axleback for several months now and I'm quite satisfied. The aggressive, deep tone sounds great and although it's a little on the loud side, I don't mind it. However, at highway speeds (60mph-75mph) the drone was unbearable for those in the back. It was almost impossible to have a conversation without yelling at each other.
Over the weekend, I recently installed the UR cat-back with the resonator and mini-muffler options. I'm extremely pleased with the in-cabin noise as the drone is no longer there [even at highway speeds]! The loudness of the exhaust has also decreased in-cabin. The best part is that from outside it sounds the same, if not better!
For those who enjoy a rather quiet in-cabin with no drone while still producing the deep aggressive tone from the outside, I def recommend both the resonator and mini-muffler.
Hope this answers some questions.