Differences in sound as related to watts?

If I understand "bigger sound," then louder is not the same thing. More watts will give you louder, but not bigger. To my ears a big or full sound is accomplished with a balanced, flat frequency response. Too often speakers have a boosted mid-bass and lower treble. This causes the upper bass and lower midrange, the "meat and potatoes" part of the spectrum, to sound relatively weak. Making everything louder will not flatten the response.

Some people equate bigger/fuller to a more resonant sound that 'fills' in the gaps. Either way, I think this is a speaker issue, not the amp. Take some time, do more listening to other systems and speakers. This will help you learn how to get the 'big' sound you want.

What exactly does ‘bigger sound’ mean to you?

Louder? Larger sound stage? Bigger images?

There is such a thing as too big, btw. When things become disproportional the mind will work harder setting things to order and listening can become tedious.

There’s also too loud, Btw…. Regardless the ease with which the music is being delivered… SPL is SPL. Your ears don’t care how sweet the sound is and it could wind up being like sitting on the beach during an overcast or partly cloudy day with a steady 10 – 12 knot breeze… you get a bad burn then, but you don’t feel the heat doing it.

Later on you will.

The relationship between efficiency and power is predictable. Impedance will play a good part in it too. there are charts online which will define how much power is required for exactly which SPL at a speakers rated eff.

Your room alone will dictate to what degree or just how large a sound you’ll be able to get away with more than anything else. In this instance… I’ve found little predetermined info regarding what sized speaker for what sized room… but it seems more a coincidental or intuitive aspect than anything else.

EX. Focal grand utopias in a 10x12x8 room probably isn’t a very good match…. Or a pr of stand mounted two ways in a 30x25x14 room likely isn’t going to satisfy…. Regardless the amps driving them.

Shoehorning too much squeakerage into a room will congest the sound, too little will lean it out.

Power itself plays a far lesser role than does the room, yet each have significant roles.

"But I think to get a "Big Sound", you need "big speakers"

I agree in general. You need this in particular for the low end. Using subs is a good strategy to lower cost and fit smaller speakers otherwise into a particular room. Large speakers are often not a good choice for smaller rooms in that they are hard to place optimally and imaging, detail and sound stage accuracy can suffer listening to many larger multi driver designs nearfield. So you need to fit the system to the room and make sure the amp is able to drive the speakers optimally at desired volumes.

Yeah efficiency and your room size and how loud you play.More likely to damage speaker by clipping an amp than running it with price greater than recommended rage though this has it's limits of course.But point about say lager "sound stage" isn't going to happen with same speakers and more power necessarily.But some speakers though like Maggie's,Sonus Faber's,B&W's etc can run on "X" but when you feed them copious amounts of power they come into their own.
Chazz

Generally, very generally, more watts means means tighter, not bigger.