About processors, I note that Hamilton is selecting CPUs with 512K caches, which is a good thing. Intel is not marketing their PIII parts with the larger L2 caches, although they are really supposed to perform rather well. If I understand correctly, web servers tend to thrash cache and having larger L2 caches makes a substantial difference.
I'm rather surprised that you can cram a DDS-4 internal tape drive into a 2U chassis, but if you can, well, that's a great solution. If your drives are also going to be on a RAID controller, I am wondering why you've selected a 2-channel Ultra160 SCSI controller for the tape drive. Also, I'm a little more tempted to keep a rather expensive peripheral like a DDS-4 tape drive as an external device, simply because a fine resource isn't utterly tied down to one machine. But that's just me.
Personally I'd be more tempted to stick with a bunch of 9GB Ultra160 drives, but I don't know how many drives your 2U chassis can hold.
Red Hat Linux 7.2 is out. You can pick up a set of installation CDs for $4 at www.cheapbytes.com. RH 7.2 has ext3 support in the kernel. If you compile your own from a recent version, it's pretty darned easy to patch in ext3 support (the ext3 code was merged in 2.4.14-pre2 apparently).
Patrick's right about RAM. It's cheap now, so you should think about a gig of quality ECC stuff. If there's anything you should consider losing, it's the hot-pluggability of your hard drives.
