i'll probably get banned for saying this here, but Nothing is more faster and secure then Mac G5. you know the old saying, "you get what you paid for." that Mac G5 you listed there, will last you for at least 4 years of top usage and you don't have to worry about virus, worms, and all the other nasty PC stuff.
You're half right. Macs are damned good machines for AV editing. However, if they were at the top of the heap as far as OSes go, then you'd probably see just as many bugs/security holes as Windows.
If all I needed this machine for was content creation/video editing, what PC components can I put together for $2300 running Adobe Premiere Pro/Elements that will outperform a PowerMac G5 Dual 2GHz w/ 1 GB RAM (for about the same amount of money) and running Final Cut Express HD?
Well, if all you're doing is AV productivity, then I would recommend going to the Mac G5. If you want to do more, especially gaming, then I'd recommend a PC.