Sounds very nice! Thats a bit larger than my garage. And, thats exactly how I'd like to heat it too! Warm floors are sooooo nice, I'm quite jealous.
Had you not ordered the materials yet, I would have suggested doing a
mooney wall setup instead of a conventional 2x6 construction. It probably would have saved you a few bucks plus been better insulated. This is most likely what I'll be doing.
What are you planning on using for roofing material?