This is a fairly simple trick that I just found; figured I might as well post it. It uses two pieces of online content- the ever-abusable Dominant Ideal Ardent ACF,
and one feat called Fortify Power
that's originally from a Dragon magazine, but since it was featured in the Mind's Eye I think it's as much 1st-party as the rest of the web stuff.
...Actually, that's it. An Ardent 10 with Dominant Ideal and Fortify Power. Fortify Power costs 2 PP to use, and only increases variable numeric effects by a quarter (half as much as Empower Power, which has the same PP cost), but it's stackable without limit. The practical limits on its stacking are that PP cost and the requirement of expending focus (which, under normal conditions, makes this pretty much always worse than Empower Power), but Dominant Ideal removes both of those- it takes zero PP to apply, and doesn't cost focus. Since the stacking is otherwise unlimited, it can be applied an arbitrarily high number of times, for arbitrarily high multiplication. The simplest application would probably be Dominant Ideal (Energy) for arbitrary damage, but there are plenty of other powers with different variable, numeric effects.
Am I wrong with any of this?