I'm adding a second GPU, an ATI 2600XT, to my 2006 Mac Pro. I already have an ATI 3870 in slot 1 (16X), and a USB/FW card in slot 3 (1X). My question which would be the better option. slot 1 (16X) ATI 3870 slot 2 or 3 (1X) an USB/FW card slot 4 (8X) ATI 2600XT or slot 1 (8X) ATI 3870 slot 2 (8x) ATI 2600XT slot 3 or 4 (4X) USB/FW card I can't see the 3870 actually needing 16X, but I don't know that I'd gain anything by running both at 8X either. The other benefit of the first option 16X/8X is that it puts more space between the 2 cards which may help cooling. Any ideas or is it a case of 'six of one, half dozen of the other'