This should answer part of your question (whether it will work at all).http://www.tomshardware.com/forum/197632-28-will-work-slot
Please pay attention to the voltages section of the thread so you don't fry anything by mistake, but you should be okay as you are using a newer system.
As to how fast, there is only one way to find out. RAID 0 will be faster than RAID 1 though.
If you can live without video speed, go with a PCI video card and swap out the PCI-X card for a PCIe card.