Travis,
I'd suggest spending some time here -
Home Energy Saver. It will take a while to enter all of the data, but you will get a better overall picture of your home. The Home Energy Saver also has pretty detailed ROI info on a variety of possible insulation / efficiency upgrades.
It's very frustrating to look back on a recent project and realize what you would have done differently if you had only known a little more. All I can say is, do the different ROI calcs NOW and you'll know how to approach any new projects.
FWIW,
Tim