Quick Question

Please forgive me for asking but I'm new to all this.

I don't understand ohm ratings.

I have a pair of "4ohm" GMA Callistos and I'm looking into match them up to a amp. One of the amps I've been reading about is a Vacume Tube Logic IT-85. This amps load setting for speakers is 5ohms. But it also says the amp will produce 80 watts into 4ohms and 60 watts into 8ohms.

Basically all I need to know is if this amp will be a good match or not? If anyone has a simple explanation for comparing ohm rating please fill me in!

thanks!