With a good PC your turns (at least up to turn 40) should take less than 5 seconds, so yes, there is a large improvement with a new PC.
I have a Intel E6600 Dual Core with 2GB and a X1900XT here and can't complain about the speed of the turn generation at all.
But random map generation still takes some time
CharonJr
PS: Turn generation speed was taken from a fairly small map (100 provinces with just 6 AIs).