I just verified the performance among below HDD conditions, may it help you to do choice.

In my Intel P4P800 system, there is a Ultra ATA controller, a SATA150 controller, and a LSI SCSI card. The HDD were run in below mode.
ATA -> Ultra DMA 5.
SATA -> SATA 150
SCSI -> U320.
SCSI -> U160.

Under the test of Intel IOmeter, I got the transfer rate as following.

ATA HDD - 83MB/S
SATA HDD - 103MB/S
U160 HDD - 95MB/S
U320 HDD - 172MB/S

Currently, SCSI U320 run fastest. then SATA. But the SCSI card must be plug into PCI-X slot. If your mother board did not have those slot. Then you could choose SATA solution.

I also run the test on U320 with RAID 1, the performance is very bad. But SCSI's RAID function is still much better than SATA's.

I did not recommend you set RAID0 for your HDD for reliability reason. It's not safe.