Hara and bb are right, if you have a 4 or even 8 drive raid 0, then the data is spread out evenly on those 4 or 8 drives. Your data will go 4 or 8 times faster, but if one of those drives would happens to fail, 7 drives of beer on the wall.. er.. I mean.. you will lose everything. And when you have that many drives, you have to keep in mind the possibily of one of them dying. Even with a ups, your chances of one of your drives dying can make you pull out all your hair if there's any important data on there.
I was looking at raid 0 only because I already have a fairly large raid 5 to store important stuff, but I wouldn't reccomend it for storing any information you don't want to lose.
But we've gotten off topic; we've started off trying to help ben make up his mind between a couple of drives. If you don't need speed, then I, personally, would opt for a 160Gb eide for nearly the same price as the sata. From what I've read, I don't believe that the serial ata's are all that much better than EIDE, yet.
this site compares a seagate 120gb SATA to a maxtor 80gb EIDE, and it looks like the SATA gets minimal speed increases an has much more cpu utilization.
http://www.lanaddict.com/review.php?ID=57
does your board come with a built in SATA controller?
just mah humble opinion.