i dont know about the maga huge cities but i just bought a new dell along with sc4 and this i can tell.
i have no problems with running the game. though... you will see some some mosaic when zooming in on a fully built city.
a better vid card and more ram (i assume) would help.
my stats are:
3.2 640 intel with HT.
1gig samson 533mghz ram.
x600 ati 256 pci-e video card.
soundblaster x-fi
160gig 7200 rpm hd
dvd rw drive.
as i said.. the only thing that seems to be outof place would be the processing of the lower texture into higher bit textures when zooming out from the full zoomed out view into the next few zoom distances.
the medium to close one there are no problems.
hope this helps.