Block size: 8K or 16K?

I am going to compare a 16KB PostgreSQL system to an 8KB system. I am working
on the assumption that 16K takes about as long to read as 8K, and That the CPU
overhead of working with a 16K block is not too significant. 

I know with toast, block size is no longer an issue, but 8K is not a lot these
days, and it seems like a lot of syscall and block management overhead could be
reduced by doubling it. Any comments?

The test system is a dual 850MHZ PIII, 1G memory, RedHat 7.2, 2 IBM SCSI 18G
hard disks, intel motherboard with onboard adaptec SCSI ULVD.

Besides pgbench, anyone have any tests that they would like to try?

Has anyone already done this test and found it useful/useless?