Agree with the need for break in. One thing to check and I speak here from personal experience, check that the ground is tight on that new line. When our house was built, I had the electricians run 10 gauge Romex to my listening room. After some time had passed and things should have been sounding pretty good, I opened up the 200 amp service and found several loose, and I mean loose grounds. Correcting that made a huge difference, especially dynamically.
I am interested to hear how things go as your line has run-in time.