No need to rush. I rebooted my system to load SMBIOSResolver (which didn't work, incidentally), and the performance problem went away! Now its speed is comparable to the 1.9GHz iMac G5 which I've had for years. I'll see how it fares as the updates are installed.

I suppose it isn't necessary to incrementally upgrade the system as the same kexts will be injected into each upgrade package anyway. I guess I'll have to activate TM before the jump.

Thanks again for all your work, Z!

AMD 64 3000+
Gigabyte K8-NSC-939
1GB RAM