Mac Upgrade Opinions?

My personal Mac (B/W 450 RevB clocked to 500) is not long for this world.  Power supply's flakin' out, one dead USB port and a CD drive that sounds like a rock-polisher.
I found this for sale by a private party.

G4 1.25 Dual (MMD)
512Mb RAM
100Gb hard drive
Radeon 9000 graphics card (and yes, I'm gonna pull it and use it as a door stop).
SCSI II Ultra PCI card.
OS 10.2.mumble, no software (not an issue, not an issue).
It's immaculate.  Been sitting on a doctor's receptionist's desk.

Is $800 US reasonable?

That is a good price. I've seen that going for about 1000€ in Finland. PowerMac G4's are the most upgradable Macs, you can change the graphics card and everything.