@Samson
PCI-E 1 & 2 share 16 lanes and PCI-E 3 & 4 share another 16 lanes, so as long as there is one VGA in 1 or 2 and one in 3 or 4 you are fine.
There are exceptions though. If using 3 VGA's in 1, 2 and 3, 1st will run @ 16x while 2nd and 3rd will run @ 8x. Also if you have VGA @ 16x and stick in some sound card for example in near slot @ 1x, you won't slow down VGA, IIRC.