What does moving from a 150 watt amp to a 400 watt amp get you?

about 3db, is the difference....but it generally seems like more.

I'm messing with a DC capable amp that can put out an approx 1.5 horsepower (1100watts) into the 4 ohm speaker load I'm running. Custom skaaning drivers, and so on. I'm kinda scared, a bit. One mistake and ..thar she blows...

The bulk of compression effects is now on the speakers. I was using 150 wpc before, and the amp  was working for it. the 1.5hp is not working for it at all, and can easily exceed the capacity of the speakers to hold themselves together.

One generally has to re-orient their thinking a bit, when putting extreme power into a 'standard' sort of speaker load. To go back to tube preamp and high power SS amp pairing, kinda thinking. Like driving rear wheel drive extreme horsepower cars, in the winter. Every move is clearly calculated in potential and in motion.

A much larger electricity bill :)

Louder

If you add a great sub to any speaker, you automatically need only half as much power for the speaker. If you bi-amp, same thing for the m/t drivers.

I have Revel Ultima Studio 1's and have half a dozen Power Amps. They are not a difficult load, but the more high quality Watts/Current you put into them the better they sound.  I've ran them with Amps 150 W. up, they just seem to lap up more high quality Wattage. They sound best with the Vincent SP-998 Mono Blocks, conservatively rated @ 300W 8ohms, 600W 40hms, 50W Class A. Everything just opens up, grip on bass, dimensionality, soundstage, bigger more powerful, more control,more musical, everything.

Must stress, make sure they are high quality Watts/Current. not just run of the mill, Parasounds, Rotel, Emotiva etc. All Watts are not created equal.