Here's an experiment you can try.
Play a single sine wave through your amp and speakers at a significant power level.
Are your speakers still OK?
Remove that tone and play one that's three times the frequency, but 1/3 amplitude or 1/9 the power.
Speakers still OK?
Add the original tone back in.
How are your speakers?
If you maintained the proper phase relationship between the 2 frequencies, you will start to approximate a square wave. If your speakers can handle that, then driving an underpowered amp into clipping will not damage your speakers.
You can repeat the above with 5th, 7th and as high as you wish to go. As you do that, you will get ever closer to a square wave but you will not be adding significantly to the power.
Bottom line, if you're blowing speakers, it's because you're driving them with too much power and not because an underpowered amp is clipping.
BTW, that square wave Wikipedia page I linked to has a 1 KHz square wave you can listen to. Does playing that blow your speakers? Mine are OK.