To the OP...
Your system seems fairly robust , except I would increase the memory to 4 gig minimum (if the operating system has to page into and out of your memory , it will throw usage to 100% ).
It has also been shown that if your system needs to be defragmented , it will make a large difference ( specifically , the disk with Calibre library. But I would not neglect the OS disk as well.
Last edited by Stumbl; 02-15-2011 at 11:56 AM.
Reason: added page file info