Differences in sound as related to watts?

"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.

I appreciate all the help. It seems that the concensus is speakers. I remember sometime ago hearing B&Ws that sounded big. Can anyone comment on that. Thank you.

In reading through the thread I don't see where there's a consensus about speakers. Although several people have asked you to explain what you mean by "big sound".