I take objection to the term "hacker" as used in the above post.
Hackers are my biggest fear. They are terrible, and they will exploit (and damage) any software setup they can get their hands on. That's why I plan to back up everything daily. (It'll be done automatically) Have you guys had many hacking problems?
The term you're looking for is "cracker". Hackers are the people that bring forth wonderful works in the tech field. The term "hacker" predates computers and refers to one who is skilled in thier craft.
Ahhh, screw it. Media has ruined the terms. I just like to nit-pick.
But to answer your question, yes I've had my run-ins. That's why I run VPS systems and place each site in it's own chroot'ed environment. If a user account gets compromised, they have minimal chances of breaking out of the chroot jail (if they really notice it IS jailed), and then I just have to review logs, restore the user filesystem from backup, and patch the hole, which is usually caused by a user script.
That PC isn't a bad start, but you might bump it up to 1GB memory, and check with the colo if they use gigabit ethernet or just 10/100. If they use gigabit, invest the extra and get a good NIC. That way you're communicating full-speed with thier routers and delivering optimum rates to your box.
What OS are you looking to run?