Off-topic:scsi vs sata/speed

[Insurance Squared Inc.]

We're finding nutch slightly slow when doing searches, I'm trying to 
find the least expensive route to speed things up. 

I swapped the server out from SCSI drives because we ran out of space.  
Instead I threw in a couple of Seagate 300gig SATA hard drives with 
software raid 0 so that I have enough space.  Now I'm wondering if that 
was the right decision.

Am I likely to see a noticeable improvement in search speeds if I yank 
out the SATA drives and throw in two 147gig SCSI drives and use software 
Raid 0?