Best answer by ratty
I don't imagine you'd want to butcher your A5s. (I certainly wouldn't take a knife to my A2s.) And separate level control of the A5s would be sacrificed if you were to be so rash.
Google "speaker to line level converter". You should be able to find something to piggy-back on your existing speaker connections. You'd preset the relative volume of the A5s via their own control. Thereafter they'd go up and down with your existing passives.