Power checks are symptomatic of good airmanship and its a core principle of best practice. Once you have started your engine and allowed for warm up time, take note of its engine tone and temps and pressure at 1000rpm. If there is no dedicated and annotated power check position then proceed to the hold and align within 30 degrees of your head wind, taking note of who is behind who who MAY be behind you. By proceeding to the hold line and not turning, you are entering the blind spot where unless you have rear windows or a bubble canopy, you won't see who is behind. Good SA includes consideration of vehicles, (ops) and other aeroplanes. Before the power check commences, take note of the wind sock.. if there are gusts then they may be responsible for slight variations in RPM once you have set the higher engine manufacturer recommended power settings. If you are normally aspirated, and once temps and pressures are set, check your carb heat before those magnetos, so you can ensure that any mag drop is not down to icing and if necessary, repeat the carb check after the magneto check. Low RPM idle and recovery to 1000rpm should be smooth and you can take note of the audible engine tone you noted at engine start. Pre take off vitals must be done before Runway entry and that goes for the power checks too btw. Even if its the second or more sector of the day and confidence prevails in your engine, carrying out a mag or carb check on the roll is both poor airmanship and folly, since the roll is all about aircraft direction, airspeed increase and positive power settlement..NOT vital checks. Aborting a take off for something that should have been identified at the hold may well compromise traffic on short final, aircraft following and occupy runway time as you clear…so think AIRMANSHIP!!!…phew!