Do your uncle's speakers sound better because he can crank them to a higher volume without the distortion you get when you do it?

Different manufacturers use different schemes to rate the power of their amplifiers. That's probably the reason for the request for the brand and model number of your amplifier. For example, a couple years back Denon took to rating their amplifiers' power at 6 ohms instead of 8 ohms. You get a larger number of watts when you do that, so it makes it look like they have more powerful amplifiers when in reality they don't!

Another thing that effects how speakers sound is their placement within a room, and the acoustics of the room. If your uncle has a room with better acoustics, and he's placed the speakers well, then that could be at least part of the reason why they sound better.

I know someone who bought a Bose 2.1 system because he thought it sounded great in the store. I was visiting him and he pointed out to me that he thought they'd sounded a lot better in the store. The next day when he was out of the house I did some experimenting with speaker placement and managed to get them to sound a lot better just by moving them a few feet. I was of course limited by his room layout. I didn't want to wear out my welcome by rearranging the furniture, too! The next day he moved the speakers back to their original location. I didn't say a word.

As far as I'm concerned, furniture placement comes in second place. Speaker placement comes first. In other words, I'll rearrange the entire furniture layout to get better room acoustics, WAF permitting.