Suggestion.
If you do not want to shell out the cash right away for a PCIe controller card, you can still get some great benefits with a controller card on on a PCI bus. The 29320lpr is a simple single channel raid card that is PCI and PCIx 133 compatible. And you can find them anywhere for about 160 bucks. I plucked mine off ebay a while back and had it on a standard PCI bus for a few years and had good performance, now I switched it onto a PCIx bus with even better results. www.scsi4me.com has that particular card, as well as others, he's and ebay seller too.