This will probably be far more info than you need but that's what happens when you ask an EE about Ohm's law.
The "Ohm" rating you see is a reference to the resistive load of the speaker. The lower the rating, the less resistance and the more power delivered, assuming current and voltage remain the same. The basic equation that governs this is Ohms Law:
V = I * R
Where V refers to the voltage potential between the two terminals, I refers to the amount of current flowing through the load and R is the resistance. Power is defined as such:
P = I * V
Plug the first into the second and you get:
P = I^2/R
As such, the lower your resistance, the more power you'll draw from the system. The electronics in your receiver have a set ability to deliver power. If you try and pull too much, you'll fry the components. Thankfully, all receivers (at least all of which I'm familiar) have internal circuitry to prevent the receiver from trying to output too much power. As such, most will simply turn off if you attempt to pull too much power from it.
That's why it's a good idea to look for a receiver that's rated to supply to such a small load. However, most receivers out there don't bother to spec it in their documentation but will provide to a load of this size with ease. When in doubt, ask.
Regards,
Josh
