Based on Brian's link, 100" at 12 feet is right at the point where 1080p becomes a noticeable difference. Perhaps I have been fooling myself (isn't ignorance bliss, especially when it means all that extra cash in my pocket?), but in any event, my advice stands true.

Since you've already got the PJ and cables run, I would live with it for a while and see what you think. At the very least, it will help inform your buying decision on the upgrade.