Tuning a system

I have a question with regards to "tuning" a system. I recently down loaded a 60 hz 0db cd and measured the amps (2) (one for the highs and one for the lows) AC output voltage with the HU at 75-80% and all internal EQ settings off. The system sounds good.

However, I am adding a Clarion external EQ that has base boost along with gain settings for the highs (front output), it also has a volume control on the EQ. How do I go about setting the system parameters with the EQ in line?

Do I leave the HU at the 75-80% volume mark and just use the Clarion volume control? IS there a way around that since the EQ is not really within hand reach? Also, do I need to remeasure the voltage output if I up the gain for the different frequencies on the Clarion EQ? Thoughts? Thanks!