Seems your the only one getting all bothered around here. Everyone else is just saying that they have used many machines in the past and 23 hp should be plenty. Everyone has said there must be something wrong with your mower. You don't seem to care about that, just saying it needs more power.
You also need to consider the torque these engines have not the horsepower. For instance the kawa 26 hp EFI has the same torque as a kawa fx 691 22 hp. And the fx 801 only has 6 ft lbs more torque more the 691.
23hp on a 54" and a 52" deck right here. Never had a problem with either machine having the power it needs. I also don't bush hog with it. I suppose if you do bush hog you'll need that bit of extra power. Otherwise you'll never see it or need 35hp on a 54" or 52" deck.