said by Draiman:
I went back and looked at the garage door quote. It's R8 not R9.7. Still decent for a garage door I think.
Not really that much difference, but you can't change the R value later (you change the doors...but best doors I've seen are R12 AND PRICEY). You can insulate the garage ceiling and walls enough, and make sure you have decent seals for the doors. That should be enough even for an upstairs office/den.
GOOD LUCK! Looks like a nice garage addition/improvement!--