It really depends on your goals, what are you looking to accomplish? My thoughts tell me to tell you to run Khan alone however up until two days ago I ran Stark and Khan together.
How many loops did you do through the night? What were the results?
You’ll see the same results I believe, masked or ultra sonic. I always use ultrasonic and through the night too, I don’t like using up my day to listen to subs because sometimes I have to choreograph and use my phone for other things.
Look in the News and Update section (I think that’s what its called) - it tells you how many loops you should do for a single title. If you plan on leaving Emperor behind for Khan this will be useful.
Currently there isn’t a stacking article available - it’s in the making but we’re waiting for it to be posted.