have like 500GB per month to backup, and not so much time on my hands, and a
Backing up 500GB/month, man you should seriously consider a large tape drive.
Now for the questions, are you backing up the entire system? or just data? I cannot fathom 500GB a month on a (how did you put it) standard consumer level PC. If you are backing up the entire os then maybe you should consider just the data.
John -- Registered Linux User 263680, get counted at http://counter.li.org