CS - As far as I know, the CAAD10 comes with 105 at the lowest level. Also, I paid $1000 for my 2009 CAAD9-6 with Tiagra in November 2008, brand new. Whatever CAAD9 you're looking at is a leftover from 2010 or earlier.

If I were in your situation, I'd go for the CAAD8 or CAAD10 with 105, depending on how much you can swing in the budget.

Also, since this is your first road bike, buy it from a bike shop. If you do and have problems, the shop will make it right. If you don't and have problems, you're on your own - you get to pay for whatever repairs/adjustments are required.