Before we go any further, are you sure you want to go SCSI? It's far from cheap, far from quiet and far from simple.
Anyway, standard health warning out the way, here's what you'll need:
A controller card, preferably a U320 one but here's the first problem, you'll only get one in PCI-X or if you look hard there are some PCIe 8x ones about. The PCI-X ones usually fit in a normal PCI slot but will be bandwidth limited to 133MB/s - don't even think about spending this sort of cash on an array that will run at >180Mb/s and go and stick it in a PCI slot. The usual approach is to go for a second hand Dell PERC4 card which is a PCIe 8x card and stick it in a spare 16x slot.
You could go for a U160 card which is native PCI but again you're going to be bandwidth limited.
You'll need an 68pin internal cable, it needs to be U320 compatible and have the correct terminator on it. A 4 head cable should be fine but it'll be £50 or so unless you can get it with the card.
Note the fact that I said 68pin. You can't get 80pin cables, the 80pin or SCA connector is a combined power and data connector used in server chassis to allow hot swapping of the disks. Adapters are available but you have to be careful, a lot of them are only Ultra Wide or Ultra2 Wide, you'll need U320 or U160 ones to match the card. Not only do the adapters split out the SCA connector to a molex and a 68pin plug they also provide a means of setting the SCSI ID for each disk which is missing from SCA drives (the server backplan provides it). Each drive and the controller need a unique ID (0-15)on the cable.
Once that's all done it *should* just be the same install routine as with SATA RAID but I'm told the Dell card can be a real pain to get going.
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