Even with a CPU of 1.5 gigs or higher, be prepared to WAIT LONG periods especially after you reach the Industrial era and beyond.
The slowness of the game even on fast new PC's has been an ongoing issue since its release.
But playing with many civs, and doing so on a real map of the Earth (not the lame ones that came with the game), is more interesting than playing on a small map against a handful of civs.