well this doesn't answer your question as asked, but here goes. I run an iMac 400MHz G3, admittedly soon to be replaced but it's running 10.2 with no problems at all. It's not the snappiest experience in the world but it's not that slow, either. OS X is just reponsive, it's great.
I would look at higher-end, simply because older processors don't cut it anymore-- try to shoot for the 867 over the 450. it'll run X pretty nicely...
pnw