I've used kent and littlesilvermax (
http://canreef.com/vbulletin/showthread.php?t=26588 ) kalk and never any problems (that I know about) with either of them.
It's possible you could have a jump depending on how much alk/cal you use in a day but the worst that will happen is that it will precipitate out and you have to start all over again. I've overdosed more then once
*edit* If you find the impellor shafts on your powerheads are getting too much mineral buildup and need to be soaked in vinegar more then once every couple of months then you are adding too much kalk