I cannot fully answer the question as we only have Hayward's P4 in store, not the aquatrol.
But Hayward's cells, the Turbo-Cells can be upgraded on a P4. Since the system is far more complex, however, it might be able to recognize the cell (like your computer recognize new equipments plugged in) and adjust the current sent to it accordingly. I strongly recommend you to communicate with Hayward's customer service and post the answer.
