Digital BW, The Print

I'm about to build a new PC for working on large images (500 MB) in
Photoshop, and trying to decide between SCSI or IDE disks. I know this
is fairly off-topic, but I respect the members of this group, and many
of the images will be B&W, so be nice.

The IDE setup could be a Western Digital 100G 7,200rpm (with 8MB buffer)
as the system disk, plus a RAID-0 array of two 40G 7,200rpm drives for
the scratch disk. Or, for about $400 net cost increase, I could use
smaller but faster SCSI disks: a 73G 10,000rpm system disk and an 18G
15,000rpm scratch disk. 

I think the biggest advantage of the SCSI disks would be faster access
times, but I don't know how much faster the SCSI machine would really be
in practice, because I don't know what size data blocks Photoshop reads
and writes to its scratch disk. Can anyone help?

Either way, I'm thinking of an Athlon XP 2000+ CPU and either 1.5 or 3 G
of DDR memory. Thanks for any advice, or pointers to good info (I have
searched).

Richard Wolfson
rwolfson at LyricDesign.com