Lena,

Sounds like there could be several things going on here. It is entirely possible that you are shaking the walls/ceiling, which could be causing the problems. If you can put the speakers on stands, that may help. If you still have problems, you may be pushing the speakers too hard. With smaller satellites, that can be a problem. Still, if you have them crossed over to a sub, they shouldn't be getting much low frequency information. Maybe you really are pushing them quite hard?

As a general rule of thumb, bigger speakers can handle power better. Maybe that's too broad of a statement, but it generally holds true. In the case of tweeters, most are about the same size, so different approaches are taken to make them more durable. The biggest is ferrofluid cooling. They actually fill the voice coil area with a fluid that helps dissipate the heat. It also provides some mechanical damping, but that's another story.

In your case, I don't really think what you necessarily need is a higher effeciency speaker. That's really only necessary when you have a whimpy amp, which you obviously don't! You need something that can take the power. If you want to keep the speakers relatively small, go with a bookshelf speaker that has atleast a 5-1/4" woofer. 6" or larger would probably be even better. Bear in mind that not all drivers are created equal. More than likely, if the speaker itself is heavy and seems sturdy, it will probably perform the same. A manufacturer isn't going to waste money on a heavy cabinet, if the drivers are wimpy. Likewise, if the manufacturer is going to sink real money into the drivers, they'll build the whole system to that standard. I've been pretty impressed with the Definitive Technology speakers I've heard. I actually have a bunch of their raw drivers, and they are particularly well built. Their speakers seem to me to be very well built. The tower speakers are particularly nice. They aren't exactly in the budget category, but I think you get quite a bit for your money there. I also like some of the Boston Acoustics stuff. The VR-M series are nice sounding (maybe a little bright for some tastes), and are some of the nicer looking speakers out there, in my opinion. Again, they aren't cheap. I'm not particularly thrilled about Klipsch. The horn sound is a little unnatural to my ears. I will admit that their big stuff is pretty nice. Not cheap.

If you are planning to keep your next set of speakers longer than the ones you have now, consider spending a little more than you are comfortable with. Speaker technology really doesn't change (despite whatever marketing gimmicks the dealers/manufacturers would have you believe). If you find a set of speakers that sound good to you, they are going to sound good always, and not become obsolete.

Jason