I went back to the shop again today and did another test ride. The bike felt right and I really liked it so I jumped on it. The people at the LBS were different today so I made the salesman explain to me how he would size it (w/o telling him what I was told yesterday) and his explanation was very similar and made a lot of sense. He was about my size and said he wouldn't go with a 19", but especially because I am planning to ride it off-road a lot.

I pulled the trigger and got a great deal. I can't wait to take it offroad this weekend.