Woehoeeeeeeeee... Electronics class-hour!!!
Today we focus on.... takka djing!
Ohm's law!!
Which says: U = I x R
Now, what you need to know: an amp will make sure that the voltage over it's output is a (gain) times the voltage over it's input.
So, U can be considered constant here. R is the impedance of your speakes.
If R is 4 Ohm, you'd have:
I=U/4
Now, if you would connect a 2 Ohm speaker:
I=U/2
The latter case gives a current that is twice as high!! So!
If you connect a speaker with LOWER impedance than the amp expects, you'll get a higher current. If you're using the amp at high power, you will ask to much. It will provide more current than it's guts can handle, and it will die...
If you connect a speaker with HIGHER impedance, current will be lower. You won't be getting all you can get from your amp, but you won't *kill* it.
Now, for homework, you will all post 5$, and go vote for me... Details in the cave, thread NEED YOUR HELP.

For the 5$, mail me for my snail mail address.