Another way of looking at it, with PCIx slots, the farthest from the CPU is the one you get a screen to watch, it auto configures the IRQ lines ( if it detects a card in the slot so NO VGA PCI cards if you are mining ), ' dummy ' plugs ( 3 resistors in the HDMI connector, IF it has one on the card ) for the 2nd card ( and more if you have the slots ). The only potential issue is some GPUs reqire either pci slot re-wiring ( pinouts.ru has a pic for what wire to add to the pcix1 to pci x16 adapter ) for the card to not only be read, but used by the motherboard. You may also want to load a USB Bootable thumb drive ( instead of a hard drive/CD ) with Linux ( personally, i use Ubuntu ) as that cuts down the power required by the whole system.
There are alot of sellers of aluminum frames that mount the motherboard and power to a base and a riser card section for the GPUs to ' hang ' above it allowing for each PCIx slot to get an adapter and airflow between crazy numbers of video cards.
thanks thats some good advice. i dived into linux a few year ago its a nice os but i was just too fresh for it even on a user friendly version like linux mint. so i have shelved the idea for no. maybe ill take a course in linux someday but win 7 is working fine for the moment.