I just put together a home server with the following components: Asus P7F-X motherboard (onboard VGA) Xeon X3440 4GB ECC ddr3 650W PSU 8hdd
The problem is that if I add a Dell SAS 5/i SATA pci-e card I don't get any video on boot and the boot doesn't go forward. Disabling the onboard VGA doesn't help. Without adding the card system boots normally. The card is to my understanding a 4x card and the result is the same whether I use the 8x(4 lanes) or the 16x slot. I've tested this card in couple of machines and it worked on an Asrock AM2 board with onboard VGA, but produced the same no video result on an older Asus P5B board. The latter failure was likely because the 16x slot was used by the video card that propably doesn't work without full 16 lanes.
In addition I've tested a pci sata card and it works just fine.