There are 2 issues here. The first is power ratings generally. Quality amps old or new generally quote real world power ratings. Most of the current Japanese based stuff inflate their power ratings by quoting a figure at a single frequency, so their real world rating is probably less than half that quoted.
The other issue is amp quality generally. Those with a poor power supply will play loud but distortion increases dramatically as the volume goes up. Clearly that is the case with your Pioneer. If you like it loud you just need a better quality amp, not necessarily a more powerful one.
Finally, newer amps seem to offer more power generally, likely because the cost of producing power amp components is dropping plus many are moving to class D which is considerably cheaper to build. LIke most things, each year the claimed power increases to compete with other brands. Just like horsepower in cars.
The other issue is amp quality generally. Those with a poor power supply will play loud but distortion increases dramatically as the volume goes up. Clearly that is the case with your Pioneer. If you like it loud you just need a better quality amp, not necessarily a more powerful one.
Finally, newer amps seem to offer more power generally, likely because the cost of producing power amp components is dropping plus many are moving to class D which is considerably cheaper to build. LIke most things, each year the claimed power increases to compete with other brands. Just like horsepower in cars.