Also if you get an FSA you need the MegaExo version, which is for their aluminum cranks. The carbon cranks use a different size.
I second the Shimano recommendation though.
The Omega is FSA's least expensive external bearing crank I think. I haven't heard good things about the bottom bracket and I can't imagine the rings are anything special, but probably the only thing you'd benefit from by replacing the arms themselves is weight. I wouldn't bother. An entry to mid range bike which would come with an Omega probably has other things on it where your money would be better spent upgrading.