You are going to measure the PSU fan Speed/fan voltage with the Chroma loads. Later you will use the same voltage provided by a programmable PSU to spin the fan without the PSU switched on, am I right?
Thought about that, too, but I decided to go for real PC-systems. During noise testing I will stop all fans, so it should work.
I'm really interested if your anechoic chamber really works
. The be quiet! kits should be decent quality and they are easy to get.