Speaker vs. amplifier wattage matching
There's a lot of misconception going around about this subject !

You do not have to match amplifier and speaker power.

So 10 W amp with a 100 W speaker is OK

So 100 W amp with a 10 W speaker is also OK

Which of these do you think is the safest combination ???

(answered below)

What ?? But... ?

The ratings of amplifiers is usually easy to measure and also the true power they can deliver.

For speakers it is much different ! The power they can handle strongly depends on the frequency of the signal.

So a 100 W speaker could for example easily handle 50 W at 500 Hz.

But that same speaker can only handle 10 W at 10 kHz !!!

And what happens if you use a 10 W amplifier to drive that 100 W speaker and you set this combination at a loud volume ?

At loud volumes the 10 W amplifier might need to deliver a bit more than 10 W but it can't so it clips see: clipping.

And that clipping generates lots and lots of harmonic frequencies which are high frequencies. And what do we know about that speaker and high frequencies ? Right, it cannot handle that: so POP goes your tweeter !

When using a 10 W speaker with a 100 W amplifier it will not be the amplifier which will give up first (clip) but it will be the speaker, it will distort. You will hear that and turn down the volume a bit. But no clipping so a 10 W speaker and a 100 W amplifier is actually a safer combination !

Oh, and regarding the 6 or 8 ohms:

An amplifier which can drive 4 ohms is OK with 4, 6, 8 ohms and higher

An amplifier which can drive 8 ohms is OK with 8 ohms and higher, but not anything below 8 ohms.