I want to say 40mb was the standard and probably by Quantum. Looking at a dealer's sales sheet from Commodore, the A2500 came standard with 40mb as well.
Ahh... looking at TBBOAH, says 2000HD's were indeed typically Quantum, but were 52mb in size. Queer how the A2500 only got a 40mb version. I bet most people upgraded that right away from their dealer.