when they say it requires 1.8GHz they are basically referring to Intel machines........as he said, an 1800+ means that it is equivelant or better in some cases to a 1.8GHz Intel........so based on that, one can assume that yes your processor will be fine.
AMD's do more instructions per cycle......this is why they are slower in the frequency but actually do just as much if not more than an Intel.
AMD named them 1800+, 2400+, 3200+ etc..etc...to make it easier on people to let them know what it's equivelant to...3200+ is closely equivelant to 3200MHz or 3.2GHz
I don't see why a lot of people seem to have such a hard time understanding that.
Just realize when you're looking on the back of software or games, it's always in reference to an Intel since they are the more dominate company.
if it says you need a 2.4GHz CPU then an AMD 2400+ would do it