I got one with a 31Hp Kawi and it's plenty of power for mowing conditions. Bigger isn't always better or needed. They go 15mph and mow most stuff fine. It's situations that are abnormal when it lowers the rpm and that might just be a good thing to let us know we are doing something not quite right.
People show pics on Lawnsite of going through 1 foot tall grass and such. They didn't do that at full speed and adding more power isn't the answer either. Decks can only discharge so much. At a foot of grass no deck can keep up with it at full speed no matter how much power it has. It's just how many cubic feet of grass can fit in cubic feet of the deck.
More power is not always the answer.