I am not an experienced stacker, Markus, having done only two practice stacks and one "for real" (
http://www.birdphotographers.net/for...-Two-Mushrooms). That said, the research I did before selecting stacking software indicated that Zerene Stacker was my best bet. It includes two stacking methods rather than one and a retouching tool that allows you to blend multiple stacked versions plus the source files more quickly than you could do it in PS. I believe they (and Helicon Focus) have a free trial, and I definitely recommend their written and video tutorials.