Well, I have set up many tanks in the past and introduced fish right away without ever experiencing ammonia spike.
Set up 1: live sand/live rock/nutriwater/bio spira
Set up 2: live sand/dry rock/bio spira (some nitrite after a day or two)
Set up 3: bio spira/seeded filter media for QT tank (some nitrite after a day or two)
(Using Dr. Tim's one and only works differently where you are recommended to use it with some source of ammonia and wait until the levels drop and it would not be safe to add any livestock right away.)
However, there are problems associated with adding fish right away and please try to avoid it at all cause, untreated fish will most likely introduce deadly disease to your system, I could name a few....ich, marine velvet, brook, fluke etc.
It will take your new tank 76 days of fallow (fishless) to get rid of them...
So in conclusion, it would be best if you just let the tank take its course and cycle while you treat the fishes you are planning on introducing to your system after QT/treatment.(2-4 weeks)