Yup, I have 5-6 GT's per channel and I don't see that kind of a drop. If you look
here Martin made some tests and he reports his vdroop with different amount of fans attached.
Anyway, I would say that the voltage drop you're seeing on your PA2's is perfectly normal. The drop on your AQ5 is a bit strange for such a load.
Is your power supply struggling maybe?
Kind regards,
Boris.