I would say it is within margin of error of a huge processor/ram upgrade.
I went from a PIII 450 and 256 megs to a XP3200 and 1GB ram and I was shocked.
I feel the same way about the Raptor, after the Raptor I would say the hard drive is the most neglected performance piece of hardware in the machine. Save the PSU money and buy a Raptor.