How fierce acceleration and braking mate? I'm expecting "mild" given your wife was in the car, but who's to say.
Could it be the ABS pump instead? That definitely makes a hammering knock when operating.
My QL compressor is almost silent when running. If it were to blame I'd reckon you'd hear it when working the suspension up and down in the driveway. Try a bit of that.
I read some stuff on the USA side regarding faulty shocks causing a knocking noise not unlike the "topping out" sound. I'm not Snuke... you'll have to find them yourself!
Let us know what you find.